Gem of Efficacious Toxin is a Legendary Gem in Diablo III. It can only be socketed into Amulets and Rings, and drops from Greater Rift Guardians.
Stats[]

Gem of Efficacious Toxin
Legendary Gem
Properties:
- Poison all enemies hit for 2000% damage as Poison over 10 seconds.
- Upgrade: +50% damage as Poison over 10 seconds (+5% per second) per Rank.
- Max: 9500% damage at Rank 150.
- Poisoned enemies also take 10% increased damage from all sources and deal 10% less damage with all attacks (Requires Rank 25)
The poison mixers of Xiansai tell of a sickly gem cutter named Zhong Yi Rou who would come by their vats and scream "I'll put you all out of work someday! Yes I will!"
Notes[]
- This gem causes any attacked enemy (regardless of the Proc Coefficient of the attack, skill or spell) to suffer Poison damage over time. This effect is renewed by further attacks, but does not stack.
- The rank 25 debuff does stack from multiple players (see example video).
- Any damaging attack made by the player character or their pets will apply the poison. However, it will only be applied on cast. As a result, DoT effects will not refresh the poisoning.
- Also note that Raiment of the Jade Harvester Set bonus does consume the Gem of Efficacious Toxin effect, but does not apply the new poisoning. As this gem does not benefit from Creeping Death and Quetzalcoatl, the damage bonus is less than it could be, however.
Tips[]
- Since this gem uses Poison damage, the only classes that can potentially enhance it with elemental damage skill bonuses are the Witch Doctor and the Necromancer.