Die Together

Die Together was a Champion-only modifier removed from the game during development. Its removal was announced in the Beta v6 patch notes in November 2011, and further explained by Blizzard afterwards.

This modifier linked the lives of each Champion in the pack, enabling any dead monsters to resurrect (with limited hit points) approximately 10 seconds after death so long as any of the other Champions remained alive.

The theory was to force players to manage the battle, and to whittle all of the Champions down to nearly dead, before trying to kill them all in rapid succession. In practice it was just annoying -- characters with AoE attacks had a considerable advantage over melee attackers and furthermore, some monsters (such as Skeletal Summoners) tended to wandering apart during the battle, making it nearly impossible to kill all of them in the allotted time.