Zei's Stone of Vengeance is a Legendary Gem in Diablo III. It can only be socketed into Amulets and Rings, and drops from Greater Rift Guardians. This gem increases damage each enemy hit suffers from attacks depending on how far from the character they are at the moment of damage being resolved. The bonus is calculated separately for each enemy and each particular hit. Upgrading increases that bonus, and also raises the maximum bonus at full distance. At rank 25, it also adds a healthy chance to Stun on hit. This chance is reduced by Proc Coefficient for every enemy hit.