Note: The final shipping legends were the product of numerous incredibly talented individuals across multiple departments and disciplines. While I initiated, implemented, and drove these character designs in terms of abilities and gameplay, the final product was only realized through a team effort.
Live Service Disclaimer: Apex Legends is a live service game. Legends are subject to balance changes and even full kit redesigns. I stopped working on Apex in late 2019 and my last Legend design released in 2020. I claim neither credit nor responsibility for the current live state of Apex characters. While much of my work survives in its original form, subsequent alterations and balance changes are the unique contributions of other designers. My commentary, observations, and philosophy on Apex character design extends to my designs at the time they launched and no further.
Live Service Disclaimer: Apex Legends is a live service game. Legends are subject to balance changes and even full kit redesigns. I stopped working on Apex in late 2019 and my last Legend design released in 2020. I claim neither credit nor responsibility for the current live state of Apex characters. While much of my work survives in its original form, subsequent alterations and balance changes are the unique contributions of other designers. My commentary, observations, and philosophy on Apex character design extends to my designs at the time they launched and no further.
Key Details
Project: Apex Legends
Feature: Caustic - Indoor Area-Control Character
Fantasy: The Monster in the Fog
Niche: Interior Chokepoint Control & Push Breaker
My Role: Pitched, Designed, and Scripted Character Abilities. Provided researched historical context for narrative team.
Released: February 4th, 2019
Feature: Caustic - Indoor Area-Control Character
Fantasy: The Monster in the Fog
Niche: Interior Chokepoint Control & Push Breaker
My Role: Pitched, Designed, and Scripted Character Abilities. Provided researched historical context for narrative team.
Released: February 4th, 2019
Kit Summary
I designed Caustic’s kit to solve the tactical problem of controlling interior spaces during building‑sieges. Drawing on the horrors of early chemical warfare, I created a gas‑based zoning system, gas proximity trap Tactical, gas grenade Ultimate, and a gas vision Passive. Together these abilities create the experience of playing a calculating evil entity patiently lurking in a cloud Nox.
Work Overview
- Pitched, designed, implemented, and iterated all three abilities. Collaborated with Designer Steven DeRose on final polish.
- Scripted dynamic gas system.
- Prototyped numerous ability alternatives to find final kit.
- Worked closely with Art, FX, Narrative, and Animation to interweave character persona with gameplay mechanics.
- Provided historical research/context for narrative team.
Designing Caustic
Design Overview
Caustic was one of my few thematic-first Apex designs. I'm a big fan of horror. I wanted to make a character inspired by horror movie monsters, while still filling a specific combat niche. Caustic is a monster looming in the fog. You can't breathe, you can't see. All you can hear is a respirator and a pair of heavy boots coming for you. It's our game's version of a horror movie hatchet drag.
Strong character abilities have an emotional tone. I wanted players to feel heartless and evil while playing Caustic. Since we were making a sci-fi shooter with a military bent, I knew I wouldn't get traction on anything supernatural. I instead opted for one of the most horrific aspects of 20th-century warfare: chemical weapons.
In Apex, attack-defense scenarios and building sieges occur dynamically as part of the mode. Our dynamic doors add nuance to fighting around doorways. You can block and break them in addition to simply opening or closing them. These nuances make the fights around building entrances substantially more interesting.
I saw an opportunity for a character to emphasize spatial control and zoning.
In the Art of War, Sun Tzu teaches that you must always select the ground on which to fight your battle. If your enemy tries to force a fight in terrain that does not favor you, deny your enemy that battle. Caustic was designed to embody this mentality.
I wanted Caustic players to engage in very specific behaviors. Caustic is like a Moray Eel. He should lurk, ambush opponents, and gravitate toward tight interior spaces. He wants to avoid getting caught in the open. In short, Caustic favors buildings and chokepoints.
This attempt to tie the character to specific level spaces is very deliberate. I felt there would be greater tactical clarity if players could expect to encounter certain characters in specific places. Learning these patterns offers players an additional aspect of mastery.
Further, I wanted to experiment with a character whose effectiveness increased over the course of a match. Caustic is most effective when enemies are trapped in his Nox gas. The more the circle shrinks, the more available play space his gas covers. He becomes extremely powerful in the late game.
To get the results I wanted, I would have to carefully tailor the abilities to meet my goals.
The Abilities
The Gas System [Shared Mechanic]
Caustic's gas dynamically conforms to level geometry. It can be blocked by doors and abilities like Gibraltar's Dome Shield.
Apex character abilities are designed to force your opponents to alter their tactics. Damage is a nuanced tool in this respect. Too much damage and the ability simply becomes a weapon that doesn't allow a response. Too little damage and opponents will accept it as a tax to avoid altering their plan. Deterrent damage lies somewhere in the middle. It's a stove hot enough to make you withdraw your hand, but not hot enough to burn you unless you keep it there.
That's the role of damage in Caustic's gas.
The gas is meant to deter and debilitate. Enemies should question pushing Caustic, and find themselves at a disadvantage if he catches them in his gas. The gas applies a movement debuff, blurs player vision, and deals damage over time. Multiple gas sources do not stack damage.
The gas damage starts modestly and ramps up the longer a player is exposed. This punishes players who stay in the gas while remaining lenient for players who quickly escape. It's a strong deterrent without being overly oppressive. Only players who ignore the gas will suffer its worst consequences.
Gas warfare requires a nuanced approach in a squad-based team game. In Apex, there is no visual distinction between "friendly" and "enemy gas." When there is visual ambiguity, you need behavioral consistency. Player mastery and competitive clarity require clean rules.
Here's the rule: Players should treat all gas as a threat. Only Caustic wants to be near gas, regardless of the source.
Caustic's gas debuffs teammates, but it damages and debuffs enemies. It's a compromise between consistent behavior and griefing potential. It was better to train players to avoid all gas than confuse them with identical visuals and inconsistent behaviors.
This tradeoff makes Caustic feel anti‑social, encouraging teammates to keep their distance and requiring careful placement from Caustic players. It’s a strong thematic fit, but it does create teamplay challenges.
At launch, Caustic-vs-Caustic fights were relatively common. Team-agnostic gas created gameplay clarity. As the roster expands, these encounters naturally become less common, reducing the impact of these edge‑case interactions.
Nox Gas Trap [Tactical]
Caustic was the first Apex character who could preemptively prepare a defense. His gas trap is roughly the size of an oil drum and triggers when enemies are in close proximity. Damage also triggers it.
I designed the traps to contest doorways and chokepoints. When a trap triggers, it produces a gas cloud that denies the area for a protracted period of time. Shooting the trap's base disables it. However, opponents can only disable traps that haven't been triggered. This is challenging when Caustic is shooting at you.
The trap's design accentuates the unique combat of building sieges. It does this by interacting with Apex's dynamic doors and building interiors.
First, the traps block doors. This allows Caustic to lock down an entrance without standing in harm's way. It also allows Caustic's squad to control more entrances without splitting up. Second, the traps serve as cover. This affords Caustic better protection when contesting enemies peeking doorways. Enemies shooting at Caustic also risk triggering the trap. Third, Caustic can see his traps through walls. He is notified when they trigger. This allows Caustic to quickly assess where attackers are breaching in a multi-floor, multi-door, building siege.
Whenever possible, I try to maximize gameplay depth while minimizing systems complexity. Caustic's traps illustrate this point. In all cases, Caustic is simply throwing a trap to the ground. When and where he places the trap is where the depth lies.
System complexity is additive, gameplay depth is multiplicative. If you want depth, focus on the interplay between a few simple systems. Depth exists in the white space between mechanics. It's specifically a measure of how many meaningful player decisions a system allows.
You can use traps to delay fights. This gives your team time to heal and threatens attackers with a potential third-party. In a three-way fight, you encourage the two enemy squads to fight by making your position less appealing to attack. Trap placement promotes strategic mind games. By intentionally leaving one door unblocked, you can funnel attackers into a prepared kill zone. Defending in depth by placing traps behind corners and door jambs allows you to set ambushes and punish attackers for overextending.
The trap's mechanics aren't complex, but the implications of where you choose to place it are nuanced. This is no accident.
The nuance is further multiplied when you consider how the circle forces player movement. Caustic rewards you for correctly anticipating how other players will move in relation to the circle.
The mere presence of the traps forces opponents to slow down. Time and circle movement favor defenders inside the circle. This hesitation to push can force attackers into unfavorable fights when the circle forces their hand. These fights usually favor Caustic.
Conversely, Caustic, like many defensive legends, is vulnerable when circle movement forces him to abandon his defensive position. I ensured that Caustic can pick up his traps to "refund" ability charges. This allows him to pack up preemptively and redeploy in a new position without having to wait for his traps to recharge. Redeploying traps also grants Caustic tactical flexibility. He can adjust his trap coverage in response to more mobile attackers.
The Gas Traps established the defensive playstyle in Apex and cemented building sieges as a unique flavor of firefight. For a deep-dive on how I used Caustic's Passive to influence player trap placement behavior, see the "Nox Vision" Passive breakdown below.
Nox Gas Grenade [Ultimate]
I wanted Caustic's Ultimate to allow for bursts of offensive aggression to contrast his mostly defensive playstyle. The Nox Gas Grenade filled that role and dovetailed well with Caustic's persona.
The Nox Grenade is one of the few cases where I designed an Ultimate that shared the same core mechanics as the Tactical. The grenade releases gas just like the traps, but at a much greater scale. I avoided this practice because ability overlap usually makes kits feel underwhelming. Caustic is an exception to that trend.
The Ultimate fills a distinct combat role. Caustic can throw his gas grenade significantly farther than his traps. While the traps require planning and patience, the Ultimate allows for sudden bursts of offensive aggression. Instead of waiting for the enemy to push, you can turn the tables. This play not only adds tactical flexibility, it mirrors the nature of a calculating evil entity with rage seething just below the surface. The Ultimate mechanically parallels a violent outburst.
While Caustic's entire kit revolves around controlling the enemy's options, the Ultimate allows you to project that control into the enemy's position. Used correctly, it forces them to panic and make bad decisions.
This concept of a forceful extension from a defensive foundation is something I learned from the board game Go. In Go, you can make an uncapturable position by arranging your pieces to create a position with two "eyes." This position cannot be captured by your opponent. From this position you can make aggressive extensions to attack enemy positions. If the enemy challenges these extensions, you backfill to your original position to solidify the extension.
The Nox Grenade Ultimate mirrors one of these aggressive extensions. The traps form a foundational position from which Caustic can extend. If the extension fails, withdrawing back to his traps provides a backstop that anchors the fight.
This dynamic extends Caustic's capabilities from pure defense into close-quarters combat. In the right hands, he can be just as effective breaching buildings as he is holding them. He can use his Ultimate to back opponents off a doorway and then establish a foothold inside the building by playing forward with his traps.
Tactical and Passive abilities typically define the core player behaviors for an Apex character's kit. In most cases, the Ultimate reinforces this play pattern. Caustic helped me realize that you can design an Ultimate that encourages bursts of a secondary behavior that complements these core behaviors by standing in contrast to the other abilities.
Nox Vision [Passive]
Sometimes, you have to design an ability to squeeze better player behaviors out of another ability.
Caustic's Passive rewards players for strong trap placement by allowing them to capitalize on their gas. It makes Caustic immune to gas and allows him to see opponents who are affected by it. Effectively, Caustic has a massive shooting advantage when fighting opponents in gas. The Passive is designed to synergize with his gas trap Tactical to encourage "positive" trapping behaviors.
A key problem with traps is that they tend to be "fire and forget." You can easily encourage players to drop traps behind them as they travel through a level. It's risk-free and easy for players to pursue this tactic. All it does is create friction for opponents. Stepping on a landmine isn't fun for anyone. This dynamic can quickly make traps feel random and annoying.
I wanted a different set of player trapping behaviors.
While you can't strictly dictate player behaviors in a multiplayer sandbox like Apex, you can influence behavior to reach a level of consistency where players can see general patterns.
I designed Caustic's traps as opportunities to capitalize. They require your presence to be effective. If an enemy sets off the trap and you aren't there to follow up, then the trap is little more than a passing inconvenience.
Caustic wants opponents trapped in gas for as long as possible. That allows him to maximize his Passive's power. A large contiguous cloud of gas is harder to escape than small scattered clouds. Caustic's most reliable means of creating large gas clouds is by concentrating his traps.
Essentially, Caustic is rewarded with combat power by performing this desired trapping behavior.
The Tactical creates the opportunity but the Passive enhances Caustic's ability to capitalize. Together, they create a surprisingly consistent M.O. Caustic players concentrate their traps where they intended to fight. They stay close by and monitor their traps for opportunities to capitalize.
I wanted character play patterns to be broadly consistent, readable, and learnable.
If you see gas traps, it should be highly likely a Caustic is nearby. This pattern helps orient fights by "announcing" a squad's fighting position. Just like weapons, loot locations, and final circle locations, I wanted characters to have clear play patterns players could identify and rely on to master the game.
Caustic was one of my few thematic-first Apex designs. I'm a big fan of horror. I wanted to make a character inspired by horror movie monsters, while still filling a specific combat niche. Caustic is a monster looming in the fog. You can't breathe, you can't see. All you can hear is a respirator and a pair of heavy boots coming for you. It's our game's version of a horror movie hatchet drag.
Strong character abilities have an emotional tone. I wanted players to feel heartless and evil while playing Caustic. Since we were making a sci-fi shooter with a military bent, I knew I wouldn't get traction on anything supernatural. I instead opted for one of the most horrific aspects of 20th-century warfare: chemical weapons.
In Apex, attack-defense scenarios and building sieges occur dynamically as part of the mode. Our dynamic doors add nuance to fighting around doorways. You can block and break them in addition to simply opening or closing them. These nuances make the fights around building entrances substantially more interesting.
I saw an opportunity for a character to emphasize spatial control and zoning.
In the Art of War, Sun Tzu teaches that you must always select the ground on which to fight your battle. If your enemy tries to force a fight in terrain that does not favor you, deny your enemy that battle. Caustic was designed to embody this mentality.
I wanted Caustic players to engage in very specific behaviors. Caustic is like a Moray Eel. He should lurk, ambush opponents, and gravitate toward tight interior spaces. He wants to avoid getting caught in the open. In short, Caustic favors buildings and chokepoints.
This attempt to tie the character to specific level spaces is very deliberate. I felt there would be greater tactical clarity if players could expect to encounter certain characters in specific places. Learning these patterns offers players an additional aspect of mastery.
Further, I wanted to experiment with a character whose effectiveness increased over the course of a match. Caustic is most effective when enemies are trapped in his Nox gas. The more the circle shrinks, the more available play space his gas covers. He becomes extremely powerful in the late game.
To get the results I wanted, I would have to carefully tailor the abilities to meet my goals.
The Abilities
The Gas System [Shared Mechanic]
Caustic's gas dynamically conforms to level geometry. It can be blocked by doors and abilities like Gibraltar's Dome Shield.
Apex character abilities are designed to force your opponents to alter their tactics. Damage is a nuanced tool in this respect. Too much damage and the ability simply becomes a weapon that doesn't allow a response. Too little damage and opponents will accept it as a tax to avoid altering their plan. Deterrent damage lies somewhere in the middle. It's a stove hot enough to make you withdraw your hand, but not hot enough to burn you unless you keep it there.
That's the role of damage in Caustic's gas.
The gas is meant to deter and debilitate. Enemies should question pushing Caustic, and find themselves at a disadvantage if he catches them in his gas. The gas applies a movement debuff, blurs player vision, and deals damage over time. Multiple gas sources do not stack damage.
The gas damage starts modestly and ramps up the longer a player is exposed. This punishes players who stay in the gas while remaining lenient for players who quickly escape. It's a strong deterrent without being overly oppressive. Only players who ignore the gas will suffer its worst consequences.
Gas warfare requires a nuanced approach in a squad-based team game. In Apex, there is no visual distinction between "friendly" and "enemy gas." When there is visual ambiguity, you need behavioral consistency. Player mastery and competitive clarity require clean rules.
Here's the rule: Players should treat all gas as a threat. Only Caustic wants to be near gas, regardless of the source.
Caustic's gas debuffs teammates, but it damages and debuffs enemies. It's a compromise between consistent behavior and griefing potential. It was better to train players to avoid all gas than confuse them with identical visuals and inconsistent behaviors.
This tradeoff makes Caustic feel anti‑social, encouraging teammates to keep their distance and requiring careful placement from Caustic players. It’s a strong thematic fit, but it does create teamplay challenges.
At launch, Caustic-vs-Caustic fights were relatively common. Team-agnostic gas created gameplay clarity. As the roster expands, these encounters naturally become less common, reducing the impact of these edge‑case interactions.
Nox Gas Trap [Tactical]
Caustic was the first Apex character who could preemptively prepare a defense. His gas trap is roughly the size of an oil drum and triggers when enemies are in close proximity. Damage also triggers it.
I designed the traps to contest doorways and chokepoints. When a trap triggers, it produces a gas cloud that denies the area for a protracted period of time. Shooting the trap's base disables it. However, opponents can only disable traps that haven't been triggered. This is challenging when Caustic is shooting at you.
The trap's design accentuates the unique combat of building sieges. It does this by interacting with Apex's dynamic doors and building interiors.
First, the traps block doors. This allows Caustic to lock down an entrance without standing in harm's way. It also allows Caustic's squad to control more entrances without splitting up. Second, the traps serve as cover. This affords Caustic better protection when contesting enemies peeking doorways. Enemies shooting at Caustic also risk triggering the trap. Third, Caustic can see his traps through walls. He is notified when they trigger. This allows Caustic to quickly assess where attackers are breaching in a multi-floor, multi-door, building siege.
Whenever possible, I try to maximize gameplay depth while minimizing systems complexity. Caustic's traps illustrate this point. In all cases, Caustic is simply throwing a trap to the ground. When and where he places the trap is where the depth lies.
System complexity is additive, gameplay depth is multiplicative. If you want depth, focus on the interplay between a few simple systems. Depth exists in the white space between mechanics. It's specifically a measure of how many meaningful player decisions a system allows.
You can use traps to delay fights. This gives your team time to heal and threatens attackers with a potential third-party. In a three-way fight, you encourage the two enemy squads to fight by making your position less appealing to attack. Trap placement promotes strategic mind games. By intentionally leaving one door unblocked, you can funnel attackers into a prepared kill zone. Defending in depth by placing traps behind corners and door jambs allows you to set ambushes and punish attackers for overextending.
The trap's mechanics aren't complex, but the implications of where you choose to place it are nuanced. This is no accident.
The nuance is further multiplied when you consider how the circle forces player movement. Caustic rewards you for correctly anticipating how other players will move in relation to the circle.
The mere presence of the traps forces opponents to slow down. Time and circle movement favor defenders inside the circle. This hesitation to push can force attackers into unfavorable fights when the circle forces their hand. These fights usually favor Caustic.
Conversely, Caustic, like many defensive legends, is vulnerable when circle movement forces him to abandon his defensive position. I ensured that Caustic can pick up his traps to "refund" ability charges. This allows him to pack up preemptively and redeploy in a new position without having to wait for his traps to recharge. Redeploying traps also grants Caustic tactical flexibility. He can adjust his trap coverage in response to more mobile attackers.
The Gas Traps established the defensive playstyle in Apex and cemented building sieges as a unique flavor of firefight. For a deep-dive on how I used Caustic's Passive to influence player trap placement behavior, see the "Nox Vision" Passive breakdown below.
Nox Gas Grenade [Ultimate]
I wanted Caustic's Ultimate to allow for bursts of offensive aggression to contrast his mostly defensive playstyle. The Nox Gas Grenade filled that role and dovetailed well with Caustic's persona.
The Nox Grenade is one of the few cases where I designed an Ultimate that shared the same core mechanics as the Tactical. The grenade releases gas just like the traps, but at a much greater scale. I avoided this practice because ability overlap usually makes kits feel underwhelming. Caustic is an exception to that trend.
The Ultimate fills a distinct combat role. Caustic can throw his gas grenade significantly farther than his traps. While the traps require planning and patience, the Ultimate allows for sudden bursts of offensive aggression. Instead of waiting for the enemy to push, you can turn the tables. This play not only adds tactical flexibility, it mirrors the nature of a calculating evil entity with rage seething just below the surface. The Ultimate mechanically parallels a violent outburst.
While Caustic's entire kit revolves around controlling the enemy's options, the Ultimate allows you to project that control into the enemy's position. Used correctly, it forces them to panic and make bad decisions.
This concept of a forceful extension from a defensive foundation is something I learned from the board game Go. In Go, you can make an uncapturable position by arranging your pieces to create a position with two "eyes." This position cannot be captured by your opponent. From this position you can make aggressive extensions to attack enemy positions. If the enemy challenges these extensions, you backfill to your original position to solidify the extension.
The Nox Grenade Ultimate mirrors one of these aggressive extensions. The traps form a foundational position from which Caustic can extend. If the extension fails, withdrawing back to his traps provides a backstop that anchors the fight.
This dynamic extends Caustic's capabilities from pure defense into close-quarters combat. In the right hands, he can be just as effective breaching buildings as he is holding them. He can use his Ultimate to back opponents off a doorway and then establish a foothold inside the building by playing forward with his traps.
Tactical and Passive abilities typically define the core player behaviors for an Apex character's kit. In most cases, the Ultimate reinforces this play pattern. Caustic helped me realize that you can design an Ultimate that encourages bursts of a secondary behavior that complements these core behaviors by standing in contrast to the other abilities.
Nox Vision [Passive]
Sometimes, you have to design an ability to squeeze better player behaviors out of another ability.
Caustic's Passive rewards players for strong trap placement by allowing them to capitalize on their gas. It makes Caustic immune to gas and allows him to see opponents who are affected by it. Effectively, Caustic has a massive shooting advantage when fighting opponents in gas. The Passive is designed to synergize with his gas trap Tactical to encourage "positive" trapping behaviors.
A key problem with traps is that they tend to be "fire and forget." You can easily encourage players to drop traps behind them as they travel through a level. It's risk-free and easy for players to pursue this tactic. All it does is create friction for opponents. Stepping on a landmine isn't fun for anyone. This dynamic can quickly make traps feel random and annoying.
I wanted a different set of player trapping behaviors.
While you can't strictly dictate player behaviors in a multiplayer sandbox like Apex, you can influence behavior to reach a level of consistency where players can see general patterns.
I designed Caustic's traps as opportunities to capitalize. They require your presence to be effective. If an enemy sets off the trap and you aren't there to follow up, then the trap is little more than a passing inconvenience.
Caustic wants opponents trapped in gas for as long as possible. That allows him to maximize his Passive's power. A large contiguous cloud of gas is harder to escape than small scattered clouds. Caustic's most reliable means of creating large gas clouds is by concentrating his traps.
Essentially, Caustic is rewarded with combat power by performing this desired trapping behavior.
The Tactical creates the opportunity but the Passive enhances Caustic's ability to capitalize. Together, they create a surprisingly consistent M.O. Caustic players concentrate their traps where they intended to fight. They stay close by and monitor their traps for opportunities to capitalize.
I wanted character play patterns to be broadly consistent, readable, and learnable.
If you see gas traps, it should be highly likely a Caustic is nearby. This pattern helps orient fights by "announcing" a squad's fighting position. Just like weapons, loot locations, and final circle locations, I wanted characters to have clear play patterns players could identify and rely on to master the game.
This video does a great job of explaining Caustic as he was designed to be played.