As of 18.20
Added 'invoke-tile-trigger' and 'destroy-decoratives' trigger effects.
Added 'trigger_effect' to tiles. It is called with the 'invoke-tile-trigger' trigger effect.

These could be used to create firewall type spells, acid patches, mines, or other interesting effects. Other spell ideas could be creating shallow water (for moats or pumps), poison clouds, lightning... Right now the only offensive spells are fireball and fire rain. These are great in most circumstances, but limit your options when facing enemies with fire resistance (like explosive biters, or fire types from bobs/natural evolution). I'd also like a "spray" type spell that continuously chews mana as you use it, and works like a wide area flamethrower... Still, this and RPG Items end up in 90% of my playthroughs, I love em so much. :D