Branding Bomb

Branding Bomb costs 2 at Sho'guul's lair.

When a bomb is dropped, it marks all enemies in the room with a brand. All non-boss enemies that have been branded are instantly killed after 5 seconds and release a red mote particle that homes in the player. When it touches them they take 10 damage per 100 max health for each enemy killed.

Since the enemies do not die directly by the player, they will not affect some countdowns (such as 's).

Trivia
The symbol resembles an inverted version of the Brand of Sacrifice that appears in Berserk, a Japanese manga series written and illustrated by Kentaro Miura.