Caustic Arrow

Borrowing a bit of toxic chemistry from the secretive Oriath Necromancers guild, a skilled archer infuses their arrowhead with a wicked venom. Once enchanted, the arrow will explode violently when it impacts a target, showering both foes and the surrounding area with a cloud of choking death. Anything living caught in the cloud will suffocate quickly, suffering heavy chaos damage until they move far away.

Description on the official Path of Exile website

Caustic Arrow is a bow attack that fires an arrow dealing chaos damage and exploding in a caustic cloud. Enemies standing within it receive a debuff that deals chaos damage over time. The caustic cloud does not poison and is therefore not affected by poison-related modifiers.

Skill functions and interactions

• Caustic Arrow will explode either at the targeted location or on the first monster or obstacle it hits.

• Multiple projectiles: additional projectiles added will cause additional caustic clouds, but debuffs from multiple clouds do not stack.

• Piercing: piercing Caustic Arrow projectiles will cause additional clouds each time they hit and will receive the chaos damage bonus any time they impact an enemy.

• Projectile damage: passive nodes and gems (such as Slower Projectiles SupportSlower Projectiles SupportSupport, Projectile
  Icon: J
  Level: (1-20)
  Cost & Reservation Multiplier: 120%Requires Level 31Supports projectile skills.Supported Skills have (20-30)% less Projectile Speed
  Supported Skills deal (10-19)% more Projectile Damage
  
  Additional Effects From 1-20% Quality:
  Supported Skills deal (0.5-10)% increased Projectile DamageThis is a Support Gem. It does not grant a bonus to your character, but to skills in sockets connected to it. Place into an item socket connected to a socket containing the Skill Gem you wish to augment. Right click to remove from a socket.) that increase projectile damage will increase both the damage on hit and the area of effect damage.

• Concentrated Effect: Concentrated Effect SupportConcentrated Effect SupportSupport, AoE
  Icon: o
  Level: (1-20)
  Cost & Reservation Multiplier: 140%Requires Level 18Supports any skill with an area of effect, regardless of whether that skill deals damage.Supported Skills deal (25-39)% more Area Damage
  Supported Skills have 30% less Area of Effect
  
  Additional Effects From 1-20% Quality:
  Supported Skills deal (0.5-10)% increased Area DamageThis is a Support Gem. It does not grant a bonus to your character, but to skills in sockets connected to it. Place into an item socket connected to a socket containing the Skill Gem you wish to augment. Right click to remove from a socket. decreases the size of the AoE and increase its damage. However, due to the nature of the skill and the wording of its modifiers, the damage increase will not appear on the tooltip.

• Point Blank: Point Blank does not affect the caustic cloud damage, it only affects projectile attack damage.

• Iron Grip: The strength bonus from the Iron Grip keystone passive does not affect the caustic cloud damage because the cloud is not considered an attack nor is it based on physical damage. The increased projectile damage portion of the Iron Grip SupportIron Grip SupportProjectile, Physical, Support
  Icon: i
  Level: (1-20)
  Cost & Reservation Multiplier: 110%Requires Level 18Supports attack skills that fire projectiles, making the increase to physical melee damage from strength also increase their physical projectile damage.Strength's Damage bonus applies to Projectile Attack Damage as well for Supported Skills
  Supported Skills deal (0-38)% increased Projectile Damage
  
  Additional Effects From 1-20% Quality:
  Supported Skills deal (0.5-10)% increased Projectile DamageThis is a Support Gem. It does not grant a bonus to your character, but to skills in sockets connected to it. Place into an item socket connected to a socket containing the Skill Gem you wish to augment. Right click to remove from a socket. will increase the cloud damage, but the strength bonus the support gem shares with the keystone will not apply.

• Accuracy: The projectile attack is subject to accuracy and can miss. However, the explosion will create a caustic cloud and do damage regardless of whether the projectile attack hit or missed. Piercing Caustic Arrow will not create additional clouds if missed.

• Duration: modifiers to duration will affect the duration of the caustic cloud.

• Culling strike: The increased damage from Culling Strike SupportCulling Strike SupportSupport
  Icon: X
  Level: (1-20)
  Cost & Reservation Multiplier: 110%Requires Level 18Supports any skill that hits enemies. If enemies are left below 10% of maximum life after being hit by these skills, they will be killed.Kill Enemies that have 10% Life or lower when Hit by Supported Skills
  Supported Skills deal (0-38)% increased Damage
  
  Additional Effects From 1-20% Quality:
  Recover (0.1-2)% of Life when Supported Skills Cull an EnemyThis is a Support Gem. It does not grant a bonus to your character, but to skills in sockets connected to it. Place into an item socket connected to a socket containing the Skill Gem you wish to augment. Right click to remove from a socket. applies to cloud damage, but the cloud does not kill enemies instantly when they have less than 10% life.

• Curses: Sniper's MarkSniper's MarkSpell, Curse, Mark
  Level: (1-20)
  Cost: (16-33) Mana
  Cast Time: 0.50 secRequires Level 4Curses a single enemy, increasing the damage they take from projectiles, and making projectiles split when hitting them, to hit other targets around them. You can only have one Mark at a time.Cursed enemies take (10-29)% increased Damage from Projectile Hits
  Projectiles which Hit Cursed Enemies Split towards 2 additional targets
  
  Additional Effects From 1-20% Quality:
  Cursed enemies take (0.25-5)% increased Damage from Projectile HitsPlace into an item socket of the right colour to gain this skill. Right click to remove from a socket. requires the target to be hit. The caustic cloud won't be affected by it. DespairDespairSpell, AoE, Duration, Chaos, Curse, Hex
  Level: (1-20)
  Cost: (16-33) Mana
  Cast Time: 0.50 sec
  AoE Radius: 22Requires Level 24Curses all targets in an area, lowering their chaos resistance.Base duration is (8.00-11.80) seconds
  +(0-1) metre to radius
  Cursed enemies have -(15-30)% to Chaos Resistance
  
  Additional Effects From 1-20% Quality:
  (0.5-10)% increased Effect of CursePlace into an item socket of the right colour to gain this skill. Right click to remove from a socket. does affect the cloud.

Gem level progression

Level			Mana Cost	Damage Effectiveness	Attack Damage	Base Duration	Chaos Damage per sec	% of Physical Damage as Chaos	Radius	Exp.	Total Exp.
1	1	0	6	55%	55%	N/A	8.8	N/A	N/A	0	0
2	2	0	6	55%	55.5%	N/A	10.1	N/A	N/A	70	70
3	4	16	6	56%	56%	N/A	13.1	N/A	N/A	308	378
4	7	22	6	56%	56.5%	N/A	18.4	N/A	N/A	1554	1932
5	11	31	7	57%	57%	N/A	27.8	N/A	N/A	6667	8599
6	16	41	7	57%	57.5%	N/A	44	N/A	N/A	26047	34646
7	20	50	7	58%	58%	N/A	61.9	N/A	N/A	49725	84371
8	24	58	7	58%	58.5%	N/A	85.4	N/A	N/A	95714	180085
9	28	67	8	59%	59%	N/A	116.2	N/A	N/A	169595	349680
10	32	75	8	59%	59.5%	N/A	156.3	N/A	N/A	283759	633439
11	36	83	8	60%	59.9%	N/A	208.5	N/A	N/A	453996	1087435
12	40	92	8	60%	60.4%	N/A	275.9	N/A	N/A	703128	1790563
13	44	100	9	61%	60.9%	N/A	362.7	N/A	N/A	1061223	2851786
14	48	109	9	61%	61.4%	N/A	474.1	N/A	N/A	2065870	4917656
15	52	117	9	62%	61.9%	N/A	616.9	N/A	N/A	2507110	7424766
16	56	125	9	62%	62.4%	N/A	799.3	N/A	N/A	5798936	13223702
17	60	134	10	63%	62.9%	N/A	1031.8	N/A	N/A	15083919	28307621
18	64	142	10	63%	63.4%	N/A	1327.6	N/A	N/A	27792735	56100356
19	67	148	10	64%	63.9%	N/A	1600.8	N/A	N/A	43869739	99970095
20	70	155	10	64%	64.4%	N/A	1927.1	N/A	N/A	242081556	342051651
21	72	159	11	65%	64.9%	N/A	2179.2	N/A	N/A	N/A	N/A
22	74	N/A	11	65%	65.4%	N/A	2462.7	N/A	N/A	N/A	N/A
23	76	N/A	11	66%	65.9%	N/A	2781.5	N/A	N/A	N/A	N/A
24	78	N/A	11	66%	66.4%	N/A	3139.9	N/A	N/A	N/A	N/A
25	80	N/A	12	67%	66.9%	N/A	3542.6	N/A	N/A	N/A	N/A
26	82	N/A	12	67%	67.4%	N/A	3995	N/A	N/A	N/A	N/A
27	84	N/A	12	68%	67.9%	N/A	4503.1	N/A	N/A	N/A	N/A
28	86	N/A	12	68%	68.4%	N/A	5073.4	N/A	N/A	N/A	N/A
29	88	N/A	13	69%	68.9%	N/A	5713.4	N/A	N/A	N/A	N/A
30	90	N/A	13	69%	69.4%	N/A	6431.6	N/A	N/A	N/A	N/A
31	91	N/A	13	70%	69.8%	N/A	6822.8	N/A	N/A	N/A	N/A
32	92	N/A	13	70%	70.3%	N/A	7237.1	N/A	N/A	N/A	N/A
33	93	N/A	14	71%	70.8%	N/A	7675.8	N/A	N/A	N/A	N/A
34	94	N/A	14	71%	71.3%	N/A	8140.3	N/A	N/A	N/A	N/A
35	95	N/A	14	72%	71.8%	N/A	8632.2	N/A	N/A	N/A	N/A
36	96	N/A	14	72%	72.3%	N/A	9152.9	N/A	N/A	N/A	N/A
37	97	N/A	15	73%	72.8%	N/A	9704.1	N/A	N/A	N/A	N/A
38	98	N/A	15	73%	73.3%	N/A	10287.7	N/A	N/A	N/A	N/A
39	99	N/A	15	74%	73.8%	N/A	10905.4	N/A	N/A	N/A	N/A
40	100	N/A	15	74%	74.3%	N/A	11559.3	N/A	N/A	N/A	N/A

Alternate skill effect

Name	Cost	Description
Tentacle Caustic Arrow EffectTentacle Caustic Arrow EffectSkill Gem EffectYour Caustic Arrow becomes an area of ethereal purple tentacles.	120	Replaces the standard effect on a Caustic ArrowCaustic ArrowAttack, Projectile, AoE, Duration, Chaos, Bow Level: (1-20) Cost: (6-10) Mana Attack Damage: (55-64)% of base Effectiveness of Added Damage: (55-64)% Projectile Speed: 3260 AoE Radius: 20Fires an arrow which deals chaos damage in an area on impact, and spreads caustic ground. Enemies standing on the caustic ground take chaos damage over time.Deals (8.8-1927.1) Base Chaos Damage per second Base duration is 2.00 seconds Modifiers to Projectile Damage apply to this Skill's Damage Over Time effect +(0-0.6) metres to radius 60% of Physical Damage Converted to Chaos Damage Additional Effects From 1-20% Quality: +(0.01-0.2) metres to radiusPlace into an item socket of the right colour to gain this skill. Right click to remove from a socket. gem with an area of ethereal purple tentacles. Preview

Related helmet enchantments

The following helmet enchantments affect Caustic Arrow.

Note that helmet enchantments are no longer obtainable since version 3.23.0 and can only be obtained in permanent leagues as already enchanted items from before this patch.

Name		Labyrinth	Stats	Spawn Weighting
Enchantment Caustic Arrow Damage 1	66	Merciless Labyrinth	25% increased Caustic Arrow Damage	helmet 75
Enchantment Caustic Arrow Damage 2	75	Eternal Labyrinth	40% increased Caustic Arrow Damage	helmet 75
Enchantment Caustic Arrow Duration 1	66	Merciless Labyrinth	20% increased Caustic Arrow Duration	helmet 75
Enchantment Caustic Arrow Duration 2	75	Eternal Labyrinth	30% increased Caustic Arrow Duration	helmet 75
Enchantment Caustic Arrow Area Of Effect 1	66	Merciless Labyrinth	16% increased Caustic Arrow Area of Effect	helmet 75
Enchantment Caustic Arrow Area Of Effect 2	75	Eternal Labyrinth	24% increased Caustic Arrow Area of Effect	helmet 75
Enchantment Caustic Arrow Wither On Hit 1	66	Merciless Labyrinth	Caustic Arrow has 14% chance to inflict Withered on Hit for 2 seconds base Duration	helmet 75
Enchantment Caustic Arrow Wither On Hit 2	75	Eternal Labyrinth	Caustic Arrow has 20% chance to inflict Withered on Hit for 2 seconds base Duration	helmet 75

Version history

Version	Changes
2.6.0	Caustic Arrow gains 1 additional unit of radius every 5 levels. No longer gain increased area of effect radius.
2.1.0	Poison Arrow has been renamed to Caustic Arrow as part of the poison changes. The damage of this skill has been increased by around 37% at level 1, but reduced by around 42% by level 20. This reduction is more than compensated for by supporting the skill with the new supports. Caustic Arrow's mana costs have been increased, from 5 to 8 at level one, and from 13 to 16 at level 20.
2.0.0	Reduced the mana cost across all levels. Now grants 0.5% increased area of effect radius per 1% of quality (was 1% per 1% quality). Damage increased by approximately 26% at gem level 20.
1.3.0	Poison Arrow can now damage totems.
1.1.2	Damage has been increased by 8% at level 1, scaling up to an increase of 75% at level 15 of the gem.
1.0.6	Poison Arrow's damage has been increased at higher levels. It now does roughly 35% more damage at gem level 15.
1.0.3	Damage progression has been increased. It is now around 15% better at level 15 than it was in 1.0.2.
1.0.2	Early levels of Poison Arrow have had their damage reduced by around 35%.
0.9.13	It now starts off around 85% stronger at level 1 and is about 1% weaker at level 15.
0.9.12	Rebalanced its mana cost progression to reflect the fact that it does damage in a comparable way to Spells.
0.9.9	The size of the Poison Arrow clouds now scale with their Area of Effect radius properly.
0.9.7	Improved the effects of Poison Arrow.
0.9.5g	Fixed a bug where the Poison Arrow cloud would appear where you clicked even if the arrow was stopped before then by a wall.
0.9.5	Fixed Poison Arrow so that damage from the degeneration is scaled properly for PvP.
0.9.4	Increased the damage.
0.9.2	Poison Arrow does more damage at higher levels than before.
0.8.7	Poison Arrow does additional chaos damage on the actual arrow itself now, in addition to the cloud damage.
0.8.5	Added new skill prototype: "Poison Arrow" (Fires an arrow which explodes in a cloud of poison. Enemies who enter the cloud are poisoned for a short time, taking chaos damage)