Cast On Critical Strike

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Cast On Critical Strike
Trigger gem
Attribute(s)Dexterity, Intelligence
KeywordsSupport, Spell, Trigger
Mana Multiplier140%
Cooldown Time50ms
Per 1% Quality1% increased Critical Strike Chance
Supported Attacks have a x% chance to Cast Supported Spells when you Crit an Enemy
You cannot Cast Supported Spells directly

Cast on Critical Strike (commonly referred to as CoC) is a trigger gem that causes a linked spell to activate when the player rolls a critical strike with the attack skill it is linked to.

The chance to cast is rolled separately for each enemy you scored a critical hit on, so it is possible to get multiple casts on one skill use if you hit multiple enemies and are lucky enough.

In case of multiple spells linked to one attack skill this support will roll its chance to cast for each spell separately, so it's possible to cast either one of them, both, or none.

Skill Functions and Interactions

Cooldown Time: When a supported spell is successfully cast, it and all supported spells of the same name are put on cooldown for 50 milliseconds. This means that a given spell can only trigger once per critical strike, and reduces the effect of linking multiple copies of the same spell to this support (especially when it is at a higher gem level). It is important to note that this cooldown does not apply to the gem as whole; you can trigger multiple spells within the 50 millisecond cooldown time as long as they are different.

Gem level progression

Level Lvl. Dex. Int. Cast
Exp. Total Exp.
1 38 40 27 50% 0 0
2 40 41 29 51% 388,734 388,734
3 42 43 30 52% 477,437 866,171
4 44 45 31 53% 583,786 1,449,957
5 46 47 33 54% 710,359 2,160,316
6 48 49 34 55% 1,355,511 3,515,827
7 50 51 35 56% 1,138,877 4,654,704
8 52 53 37 57% 1,368,233 6,022,937
9 54 55 38 58% 1,638,338 7,661,275
10 56 57 39 59% 1,956,648 9,617,923
11 58 58 41 60% 3,655,184 13,273,107
12 60 60 42 61% 3,017,327 16,290,434
13 62 62 43 62% 3,576,232 19,866,666
14 64 64 44 63% 4,231,667 24,098,333
15 65 65 45 64% 2,395,078 26,493,411
16 66 66 46 65% 8,421,063 34,914,474
17 67 67 46 66% 16,159,983 51,074,457
18 68 68 47 67% 41,170,367 92,244,824
19 69 69 48 68% 86,794,448 179,039,272
20 70 70 48 69% 157,405,063 336,444,335
21 72 72 50 70% N/A N/A
22 74 71% N/A N/A
23 76 72% N/A N/A
24 78 73% N/A N/A
25 80 74% N/A N/A
26 82 75% N/A N/A
27 84 76% N/A N/A
28 86 77% N/A N/A
29 88 78% N/A N/A
30 90 79% N/A N/A

Quest reward

This skill is given as quest reward for the following quests:
A Fixture of Fate
Act 3

Vendor reward

This skill can be bought at the listed npc vendors after completing the following quests:
The Eternal Nightmare
Act 4
Petarus and Vanja


Linking with other skills

At a bare minimum, a Cast On Critical Strike setup will require three gems: an attack, Cast On Critical Strike itself, and a spell to be triggered. This generally leaves at most three other supports that may be linked. If possible, the supports should both increase the number of times Cast On Critical Strike triggers, and increase the effectiveness of the triggered spells. Note that Cast On Critical Strike cannot trigger more than once per frame, so staggered hits (e.g. multiple projectiles) are preferred to simultaneous hits (e.g. most area of effect damage) which will only proc at most once per attack.


By far the most popular family of Cast on Critical Strike setups, projectile Cast On Critical Strike focuses on the projectile keyword. Popular attacks for this purpose include:

  • Spectral Throw: Naturally staggers hits, automatic pierce, allows the use of melee weapons at range.
  • Barrage: Causes a large number of sequential hits per attack.
  • Power Siphon: Naturally produces power charges.
  • Split Arrow: Naturally large number of projectiles.
  • Tornado Shot: Piercing on initial arrow(s) and produces three times as many subprojectiles.
  • Frost Blades: Three projectiles plus the initial hit.
  • Molten Strike: Magma balls generally hit on different frames, causing a large number of hits.
  • Lightning Strike: Three projectiles plus the initial hit.

Support skills that affect both the number of hits and crits projectile attacks generate and affect projectile spells include:

Useful projectile spells and their support limitations include:

A second spell may satisfactorily be used in place of a support.

Area of Effect

Some attacks have advantageous built-in area of effect:

  • Ground Slam: The area of effect is progressive, not instant, allowing multiple casts per attack. However, it can only get one cast against a single target.

This works well with spells which have Area of Effect component, such as:

Support gems which can benefit this setup are:


Another possibility is to use attacks to trigger minions, which benefit from attack supports. In addition to the projectile skills listed before, we have some other good choices:

  • Double Strike: Causes two hits per attack, only uses main hand when dual-wielding.
  • Cyclone: Causes staggered hits rapidly.

Minions generally have poor critical strike capabilities, so critical strike supports are not as effective as they are with projectile spells. Good attack supports include:

  • Additional Accuracy: Improves minion accuracy greatly, removes the need for accuracy on gear, and quality gives extra critical strike chance.
  • Faster Attacks
  • Melee Splash: While it does not increase procs much due to the splash happening on a single frame, it greatly improves minion effectiveness.
  • Multistrike: For Melee attacks.

Most minions are severely capped in number and thus do not benefit much from the high proc rate of Cast On Critical Strike. However, there is one that works well:

Passives and gear

Since "double-dipping" on support gems is key to an effective Cast On Critical Strike setup, having a 5- or 6-link is more important than it is for most builds.

Unlike conventional attack builds, attack damage is not necessary on passives or gear, though it can be helpful in situations where the linked spells are less effective. Attack speed and critical strike chance are the two essential statistics.

Some base item types tend to have better critical hits per second than others:

  1. Wands
  2. Claws, Daggers
  3. Sceptres, Thrusting Swords
  4. Bows, Staffs, 1H Swords

Possibly good uniques to use include:

Item Perfect crits/s
Death's HarpDeath's Harp
Death Bow
Physical Damage: (44–50 to 116–131)
Critical Strike Chance: (5 to 7.5)%
Attacks per Second: 1.21
Requires Level 32, 107 Dex(30 to 50)% increased Critical Strike Chance(100 to 125)% increased Physical Damage
10% increased Attack Speed
100% increased Global Critical Strike Multiplier
Adds an additional Arrow
The mournful music of the strings,
The creaking arch, the arrow sings.
A choking cry, a rattled breath,
The Reaper's Song, the Harp of Death.
Royal Bow
Physical Damage: (18–57 to 22–61)
Critical Strike Chance: (6.50 to 7.00)%
Attacks per Second: (1.59 to 1.65)
Requires Level 28, 95 Dex(6 to 12)% increased Elemental Damage with WeaponsAdds (8–16 to 12–20) Physical Damage
(10 to 14)% increased Attack Speed
(30 to 40)% increased Critical Strike Chance
60% increased Mana Regeneration Rate
Gain 110% of Bow Physical Damage as Extra Damage of an Element
"Toasted or frozen
Or twitching in the light
I'm not fussy
And neither is Death."
- Koralus Doomfletch
Quill RainQuill Rain
Short Bow
Physical Damage: 4–11
Critical Strike Chance: 5%
Attacks per Second: 3.00
Requires Level 5, 26 Dex+(10 to 20) to Dexterity
100% increased Attack Speed
+(25 to 50) to Accuracy Rating
(50 to 100)% increased Projectile Speed
50% less Weapon Damage
"The rain of a thousand quills that whittle present into past, life into death."
- Rigvald of the Ezomytes
Imperial Bow
Physical Damage: 19–78
Elemental Damage: (32–48 to 40–60), (1–80 to 1–100)
Critical Strike Chance: (8 to 9)%
Attacks per Second: (1.59 to 1.67)
Requires Level 66, 212 Dex(6 to 12)% increased Elemental Damage with WeaponsAdds (32–48 to 40–60) Cold Damage
Adds (1–80 to 1–100) Lightning Damage
(10 to 15)% increased Attack Speed
(60 to 80)% increased Critical Strike Chance
15% increased Quantity of Items Dropped by Slain Frozen enemies
30% increased Rarity of Items Dropped by Slain Shocked enemies
It hunts; as silent as falling snow, as deadly as the tempest.
Mortem MorsuMortem Morsu
Fright Claw
Physical Damage: (16–65 to 18–74)
Critical Strike Chance: 7.88%
Attacks per Second: 1.80
Requires Level 34, 61 Dex, 61 Int2% of Physical Attack Damage Leeched as Life(75 to 100)% increased Physical Damage
20% increased Attack Speed
25% increased Critical Strike Chance
25% increased Global Critical Strike Multiplier
(10 to 20)% of Physical Damage Converted to Chaos Damage
Poisonous Hit
25% reduced Enemy Stun Threshold with this Weapon
Fear blisters the heart and thins the blood.
Fear squeezes lungs and sets the guts to fester.
Fear is the wound left untended.
Bino's Kitchen KnifeBino's Kitchen Knife
Slaughter Knife
Physical Damage: (59–198 to 69–218)
Critical Strike Chance: (9.24 to 9.9)%
Attacks per Second: 1.40
Requires Level 65, 81 Dex, 117 Int40% increased Global Critical Strike Chance30% increased Damage over Time
Adds (50–60 to 120–140) Physical Damage
(40 to 50)% increased Critical Strike Chance
(10 to 15)% increased Global Critical Strike Multiplier
+(8 to 12)% to Chaos Resistance
On killing a Poisoned enemy, nearby enemies are Poisoned
On killing a Poisoned enemy, nearby allies Regenerate Life
Calling it poison would imply that it was even edible.
Ungil's GaucheUngil's Gauche
Boot Knife
Physical Damage: (14–54 to 16–60)
Elemental Damage: 3–30
Critical Strike Chance: 6.6%
Attacks per Second: 1.54
Requires Level 20, 31 Dex, 45 Int40% increased Global Critical Strike Chance12% additional Chance to Block while Dual Wielding
(80 to 100)% increased Physical Damage
+(10 to 20) to Dexterity
Adds 3–30 Lightning Damage
10% increased Attack Speed
50% increased Global Critical Strike Chance
Unwieldy and garish became graceful and deadly in Ungil's nimble hands.
Imperial Skean
Physical Damage: 17–69
Critical Strike Chance: 6.6%
Attacks per Second: 1.45
Requires Level 66, 95 Dex, 131 Int40% increased Global Critical Strike Chance(50 to 70)% increased Spell Damage
(80 to 100)% increased Critical Strike Chance for Spells
+10 Life gained on Kill
+5 Mana gained on Kill
10% increased Radius of Area Skills
Divine intervention feels better when you do it yourself.
War Hammer
One Handed Mace
Physical Damage: (18–42 to 21–49)
Critical Strike Chance: 6.25%
Attacks per Second: 2.1
Requires Level 20, 71 Str20% increased Stun Duration on enemies(50 to 75)% increased Physical Damage
50% increased Attack Speed
25% increased Critical Strike Chance
+(20 to 30)% to Fire Resistance
+(20 to 30)% to Lightning Resistance
"I know how to say 'faster' and 'attack' in Karui, Marak and Ezo."
- Voll of Thebrus
Doryani's CatalystDoryani's Catalyst
Vaal Sceptre
One Handed Mace
Physical Damage: (96–158 to 116–218)
Critical Strike Chance: 6.68%
Attacks per Second: (1.55 to 1.61)
Requires Level 75, 113 Str, 113 Int10% increased Elemental DamageGems in this item are Supported by level 20 Elemental Proliferation
Adds (65–100 to 85–160) Physical Damage
(11 to 15)% increased Attack Speed
(6 to 10)% increased Cast Speed
(30 to 40)% increased Global Critical Strike Chance
0.2% of Elemental Damage Leeched as Life
(80 to 100)% increased Elemental Damage
The result of the catalystic reaction would be either immortality for all, or death for all. It was a risk Doryani was willing to take.
Hegemony's EraHegemony's Era
Judgement Staff
Physical Damage: (245–311 to 255–341)
Critical Strike Chance: (7.92 to 8.58)%
Attacks per Second: (1.4 to 1.45)
Requires Level 68, 113 Str, 113 Int12% Chance to Block6% Chance to Block
Adds (180-190 to 190-220) Physical Damage
(12-16)% increased Attack Speed
(20-30)% increased Critical Strike Chance
+1 maximum Power Charge
10% chance to gain a Power Charge if you Knock an enemy Back
with Melee Damage
The Right to rule demands mental acuity,
a strong arm,
And a tenacious sense of justice.
Eternal Sword
One Handed Sword
Physical Damage: (52–107 to 72–122)
Critical Strike Chance: 5%
Attacks per Second: (1.80 to 1.88)
Requires Level 66, 104 Str, 122 Dex18% increased Accuracy RatingAdds (20–40 to 55–70) Physical Damage
(20 to 25)% increased Attack Speed
+(180 to 200) to Accuracy Rating
+(180 to 200) to Evasion Rating
3% increased Movement Speed
1% increased Attack Damage per 450 Evasion Rating
She dances a dance beneath the shade,
The twilight shroud her only blade,
Who now hears her feathersteps flowing?
Beneath the stars, the moondrops glowing.
Piscator's VigilPiscator's Vigil
Tornado Wand
Critical Strike Chance: (9.60 to 10.40)%
Attacks per Second: (1.43 to 1.54)
Requires Level 65, 212 Int(16 to 19)% increased Spell DamageNo Physical Damage
(10 to 18)% increased Attack Speed
+(340 to 400) to Accuracy Rating
(20 to 30)% increased Critical Strike Chance
Attacks with this Weapon have (100 to 115)% increased Elemental Damage
"Stone still, amidst the reeds,
breath fogging in the iron cold air.
he sits, he waits, he watches.
A piscatorial vigil, sat by the river,
his cathedral, his patience his unanswered prayer."
- Jojoba Mansell, bard, angler, adventurer

Version history

Version Changes
  • Cast on Critical Strike's cooldown has been increased from 0.01 seconds to 0.05 seconds.
  • The chance to cast has been reduced by a flat 20% at all levels.
  • Cast on Critical Strike now has a 10 millisecond cooldown. The chance to cast supported skills has been increased by a flat 20%.
  • The Cast on Crit support gem has been renamed to Cast on Critical Strike
  • Cast on Crit has been added to the game.