Temporary pit trap: it fills itself in after a certain number of turns. A monster in it will be buried. It could either use a timer to decide when to fill itself in, or be tied to the monster id of its creator, triggering after a certain amount of time if the creator is still on the level. Also a good candidate for creating during an earthquake, rather than a permanent pit.

Spell of earthquake, mid-level matter spell. Causes an earthquake centered on you; range and power varies based on your skill level.

Boots of earthquake: when you stomp the ground with them (by kicking downward), an earthquake happens. However, this spends 1 point of enchantment on the boots (not going below 0; if they are 0 or less then no earthquake happens.)