Blighter

Blighter is a Rift Guardian based off the "Herald of Pestilence" enemies found in Act III. Like a normal Herald of Pestilence, Blighter has a ranged AoE attack where he becomes rooted in place during the cast. When Blighter's health drops to 25% this attack changes so that the number of AoE circles drastically increases. If the player is fighting in a narrow area he/she will quickly be overwhelmed by overlapping AoE.