Bonus Spell #2:
Land Mine
(Introduced in this Game Geekery post.)
My friend Chris suggested some sort of delayed ground-based harassment spell along the lines of Grease or Glue, but I realized that we didn't have one that simply blew up! Happily, that's no longer an issue. And while I realize some people may cringe at the pun, I'm rather proud of it. :)
The energy cost is obviously drawn directly from Explosive Fireball, but the limit is different; where a wizard with Magery 3 could throw a 3d to 9d Explosive Fireball, he can do a 6d Land Mine. Of course, the tradeoff is that a 6d Land Mine takes half as long to cast as a 6d Explosive Fireball, and it offers far more options when it comes to setting up traps.