Firestorm

FirestormSpell, AoE, Duration, Fire
Radius: 25 / 10
Mana Cost: (9 to 26)
Cast Time: 0.90 sec
Critical Strike Chance: 6.00%
Damage Effectiveness: 30%Requires Level 12Flaming bolts rain down over the targeted area. They explode when landing, dealing damage to nearby enemies.Per 1% Quality:
1% increased DamageDeals (4-162) to (10-243) Fire Damage
Base duration is 2 seconds
One impact every 0.1 secondsPlace into an item socket of the right colour to gain this skill. Right click to remove from a socket.Acquisition
Level: 12Purchase Costs

Normal

1x Orb of Transmutation

Sell Price
1x Scroll Fragment

Perhaps the most feared area effect skill in the Witch's arsenal, the mighty Firestorm skill is legendary for its power and cruelty. The incantation tears a rift in the heavens that showers a wide swath of ground in a rain of searing flames. These bolts pound down without mercy, burning everything they touch, then exploding violently to cause even more harm.

Description on the official Path of Exile website

Firestorm is a spell that rains numerous fiery bolts in an area, each bolt dealing area of effect fire damage.

Skill Functions and Interactions

Area of Effect: Increased AoE will increase both the area in which the fireballs randomly fall and also the radius of the individual fireball damage. Full spell damage is done at any point within the AoE of a fireball, however due to the fact that enemies take up an area and not simply a point, less spell damage is dealt to any given enemy as area increases. This is why, contrary to popular belief, increasing the AoE of Firestorm decreases the average number of hits to single target.

Duration: Increasing duration with either supports or passives will increase the total number of fireballs that fall before the spell ends.

Damage Effectiveness: Damage from secondary sources like 'added damage' supports or heralds applies at only 30% of their listed value.

Damage per Second: Due to the complexity of estimating actual DPS of the skill including all possible factors, ingame tooltip shows only average damage per hit of one fireball, with actual DPS of the skill being considerably higher. The closest currently available estimate can be obtained by using the damage calculator.

Gem level progression

Level			Mana Cost	Fire Damage	Exp.	Total Exp.
1	12	33	9	4 to 10	0	0
2	15	39	10	9 to 13	15,249	15,249
3	19	48	11	11 to 17	41,517	56,766
4	23	56	12	15 to 22	81,983	138,749
5	27	64	13	19 to 28	147,968	286,717
6	31	73	14	23 to 35	250,557	537,274
7	35	81	15	29 to 44	405,086	942,360
8	38	88	16	35 to 52	447,718	1,390,078
9	41	94	17	40 to 61	615,318	2,005,396
10	44	100	18	47 to 71	834,639	2,840,035
11	47	106	19	55 to 82	1,570,760	4,410,795
12	50	113	20	64 to 95	1,633,987	6,044,782
13	53	119	21	74 to 110	2,151,030	8,195,812
14	56	125	22	85 to 127	2,812,189	11,008,001
15	59	132	23	98 to 147	5,099,360	16,107,361
16	62	138	24	112 to 169	9,400,731	25,508,092
17	64	142	24	123 to 185	15,273,366	40,781,458
18	66	146	25	135 to 203	26,286,582	67,068,040
19	68	151	25	148 to 222	62,890,590	129,958,630
20	70	155	26	162 to 243	212,046,017	342,004,647
21	72	159	26	177 to 265	N/A	N/A
22	74	N/A	27	193 to 290	N/A	N/A
23	76	N/A	27	211 to 317	N/A	N/A
24	78	N/A	28	231 to 346	N/A	N/A
25	80	N/A	29	251 to 377	N/A	N/A
26	82	N/A	30	274 to 411	N/A	N/A
27	84	N/A	30	299 to 448	N/A	N/A
28	86	N/A	30	326 to 488	N/A	N/A
29	88	N/A	31	355 to 532	N/A	N/A
30	90	N/A	32	386 to 579	N/A	N/A

Quest reward

This skill is given as quest reward for the following quests:

Class	Marauder	Templar	Witch	Shadow	Ranger	Duelist	Scion
Quest
The Siren's Cadence Act 1

Vendor reward

This skill can be bought at the listed npc vendors after completing the following quests:

Class	Marauder	Templar	Witch	Shadow	Ranger	Duelist	Scion
Quest
The Siren's Cadence Act 1 Nessa
A Fixture of Fate Act 3 Siosa
Fallen from Grace Act 6 Lilly Roth

Alternate skill effects

Name	Cost	Description
Siege Firestorm Effect Siege Firestorm EffectFirestorm Skin Stack Size: 20Your Firestorm becomes a flaming siege assaultRight click this item then left click a Firestorm Gem to apply it.	25	Replaces the standard projectile effects on a FirestormFirestormSpell, AoE, Duration, Fire Radius: 25 / 10 Mana Cost: (9 to 26) Cast Time: 0.90 sec Critical Strike Chance: 6.00% Damage Effectiveness: 30%Requires Level 12Flaming bolts rain down over the targeted area. They explode when landing, dealing damage to nearby enemies.Per 1% Quality: 1% increased DamageDeals (4-162) to (10-243) Fire Damage Base duration is 2 seconds One impact every 0.1 secondsPlace into an item socket of the right colour to gain this skill. Right click to remove from a socket. gem with burning cages of spiked metal. Preview

Related helmet enchantments

The following helmet enchantments affect Firestorm:

Name		Effect(s)
EnchantmentFireStormDamage1	66	25% increased Firestorm Damage
EnchantmentFireStormDamage2	75	40% increased Firestorm Damage
EnchantmentFirestormDuration1	66	20% increased Firestorm Duration
EnchantmentFirestormDuration2	75	30% increased Firestorm Duration
EnchantmentFirestormExplosionAreaOfEffect1	66	8% increased Firestorm explosion Area of Effect
EnchantmentFirestormExplosionAreaOfEffect2	75	12% increased Firestorm explosion Area of Effect

Version history

Version	Changes
2.1.0	Damage increased by around 20% higher at level 20.
2.0.0	Firestorm: Had a very slight damage buff. Area of effect of explosions increased by 11% (9 to 10). It now grants 1% area damage per 1% quality instead of reduced delay between fireballs. The Duration of Firestorm has been increased from 1.3 seconds to 2 seconds at all levels. Base Cast Speed has been increased from a cast time of 1 second to 900ms. Critical Strike Chance has been increased from 5% to 6%.
1.0.4	Firestorm: The radius of the area that fireballs land in has been increased by 39%. The delay between strikes has been reduced from 0.15 seconds to 0.10 seconds. Damage has been increased by 35%. The quality bonus has been reduced by 33.33% to match the reduced projectile delay.
1.0.0	Reduced mana cost.
0.11.2	The damage done by the Firestorm spell when used by all versions of Ambrosia and Merciless Fire Fury has been increased. Merciless Gravicius's Firestorm has been very slightly increased in damage.
0.11.1	Spells with Damage Effectiveness no longer have their own damage affected by Damage Effectiveness. Damage values on these skills have been updated to reflect this.
0.9.12qq	Fixed a bug where monsters in high level areas would not do the correct Firestorm damage.
0.9.11i	Fixed the randomness when it was used with Traps.
0.9.11f	Increased the damage and made its cluster tighter.
0.9.9	Fixed a bug where the damage from Firestorm would not display on the client at the right time.
0.9.6	Changed Firestorm to be affected less by additional damage from support gems. Fixed a bug where Firestorm could hit monsters through walls.
0.9.5	Modified Firestorm's behaviour so that the explosions have a larger radius and are more likely to fall near the centre of the affected area. Doubled the number of fireballs that fall and rebalanced damage around these changes.
0.9.3c	Raised the overall damage and its high level damage scaling.
0.9.3	Firestorm has been added to the game.