Baldur's Gate 3: Interesting Condition

[Part of the Cursed story line]

The warlock Wyll meets the team at the entrance to the Underdark to try slay Karlach on orders from his patron, the cambion Mizora, but is convinced not only to stand down but to join the party instead. For this he is turned by hellish magics to look a bit more devilish but it doesn't seem to bother anyone much. Especially not the minotaurs, hook horrors, duergar or really annoying bullette that attack the party members equally.

Luckily there's a friendly Myconid colony nearby and a big shroom guy named Glut helps the party clear out this zone until he is slain by a spectator (beholder type thing) near the end, but the team is free to take a rowboat down to the duergar controlled Grym Forge and again via parasite-psionics trick them into being allies for now.

Deciding to explore first the team completes the jumping puzzle to get to the forge itself, fighting animated armors on the way but it is a lava mephit ambush (and the fact they explode on death) that kills Karlach on the steps leading down to it. They opt to back off for now, which is the perfect time for Gale to reveal that his "condition" is worsening, and that he's a living bomb.