Add more explosives-based traps and throwing items-- landmines, bombs, and grenades that do not explode instantly when used... Change their behavior so that they can be set off from a distance by spell damage, other explosions, or possibly even bolts. One good solution would be to give each one its own (very low) before it explodes. Others could be primed with a timer to go off in so many turns. Huzzah! You've added new strategies to the game!
Simply adding the health to these explosions would allow for nearly everything mentioned. A curse/debuff that does Damage over time would work as a timer without needing to implement even more new features. +1 I support this idea.
Hooray! Someone else likes my idea. i was actually thinking of 100 Rogues and the robots in it. They fire rockets that slowly move towards a point with each turn, and then when they reach their target they explode in an AOE. So the player has to either get away or deal with the damage. Additionally, the explosions from these missiles expand in a way that is dependent on how open or closed the space is-- so if you're in a hallway, it will travel really far down that small space (6 or 7 tiles). But if you're in an open room, it stops after 2 or 3. Maybe we could do something like that for these explosives as well.
Hmm, for now as an alternative it may be possible to make a new monster that self destructs. It could be something you can summon but it casts a spell on itself that after a few turns kills the said monster and makes an explosion. That makes me wonder. Can aggressive monsters cast summoning spells? I have not seen this done nor heard of it but that could open some new possibilities.
Somewhere in another thread I suggested a mine-layer summon. It would act in a fashion as its name dictates. It would never attack, and would have low HP, but every turn it would lay a mine that would last a while before self destructing. This would be enhanced if the mine layer itself exploded upon death. This sort of summon would perhaps revitalize Golemancy too. (The best Golemancy summon sucks hard for the cost. If the Robot that Loves flied and exploded upon death it could be worth the cost, but as it is, the Pyromancy summon is far superior due to flight and pitifully low cost.)