Slavers
The Slavers is an Act 2 elite encounter consisting of three enemies: a Taskmaster, a Blue Slaver, and a Red Slaver. The Taskmaster deals small damage and adds Wounds (Unplayable, dealing 1 damage when drawn) to your discard pile each turn. The Blue Slaver applies Vulnerable with Rake, and the Red Slaver can Entangle you to prevent Attack plays.
The Slavers trio is dangerous due to the combination of debuffs and deck pollution. Wounds from the Taskmaster accumulate across the fight, dealing chip damage each time they are drawn. Prioritizing the Taskmaster to stop Wound generation, then clearing the Red Slaver (due to Entangle) before the Blue Slaver, is often the recommended kill order. AoE cards are particularly valuable for managing all three enemies simultaneously.