The Delmintalintar's Bomb of the Ancients is an artifact in Heretic. It looks like a floating hourglass. When set, a Timebomb of the Ancients floats where the player was standing for 40 tics, then explodes and deals damage another 6 tics later. It causes splash damage 128 units in radius, with 128 units of damage at the center.
When the player is being chased by hordes of monsters, it can be effective to leave behind some timebombs to clear them away. The timebomb also acts as a grenade, being very good at clearing rooms with weak monsters. It is overall an extremely effective way to deal significant amounts of damage.