Legendary Gem Bane of the Powerful is popular among the players. The buff after kill elites and its 25 level buff make it valuable to some extent. However, the functions depended on the elites. So, you need kill all the elite to trigger the buff. Currently there is a bug that makes Bane of the Power apply its bonus after kill illusion. Find a large selection of D3 items at the lowest prices.As for the issue, the community Manager Grimiku responded the players this is not working as intended, and it will be fixed. So read the original post on the official forum below:

"The damage bonus that’s applied by slaying Elite monsters with Bane of the Powerful functions differently depending on the Elite(s). In situations where there is a single Elite (like a Treasure Goblin or Act boss) then it's pretty straight forward in the sense that once you kill that Elite you get the buff. When the Elites are in some form of a pack, though, it gets slightly more complicated. The entire pack will need to be slain in order to trigger the buff. That includes every member of a Champion pack, or all of the minions along with their Elite master.

That said, there's currently a bug that allows Bane of the Powerful to apply its bonus damage after killing illusions, which is not intended. We'll be sure to let everyone know through the appropriate channel once that fix is implemented, so be sure to keep an eye out for it."

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