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.
For obvious reasons, using Zei's Stone of Vengeance on melee class characters is entirely pointless. This gem does affect the damage done by pets and minions; until patch 2.6.0, the distance was calculated from the enemy to that pet or minion, not to the player (therefore melee pets would not benefit from it); but this was changed to player-monster distance in 2.6.0.
Damage over time effects do grow in power if the enemy flees, or the character ventures far from the target (making the 'hit-and-run' tactics quite efficient). A chance to Stun adds some more maneuverability as well.
Zei's Stone of Vengeance
- Damage dealt to each enemy hit is increased by 4% for every 10 yards between you and the enemy hit. Maximum 20% increase at 50 yards.
- Upgrade: +0.08% additional damage for every 10 yards, and +0.40% maximum damage bonus (at full range) per Rank.
- 20% chance on hit to Stun the enemy hit for 1 second (Requires Rank 25)
Legend says this gem was crafted by Zei to torment fleeing enemies. Other legends claim that Zei never existed.