Hexaghost

Hexaghost is one of three Act 1 boss enemies with 250/264 HP. On its first turn it uses Activate (dealing 1 damage for each HP the player is missing, minimum 1), then cycles through Divider (6 hits scaling with your missing HP), Sear (adds Burn cards to discard), Tackle (multiple hits), and Inflame (gains 2 Strength). It repeats this cycle across the fight, gaining potency with Inflame.

Hexaghost is most dangerous to players who entered the boss fight at low HP, as both Activate and Divider scale with missing HP. Entering the fight at full HP dramatically reduces its first two attack values. The Burn cards it adds deal 2 damage when drawn or held at end of turn. Block-heavy builds that can weather the multi-hit Divider and Tackle attacks do well here. Managing your HP going into the fight by using potions or rest sites is particularly impactful against Hexaghost.