Ring of Ice (Warlords Battlecry, SSG 1998)
< I used to use it with my level 18 Necromancer/Summoner to take out my enemies' towers, because it did ~380 damage and I could use it three times in a row, then I could convert nearby non-aggressive buildings and use them to my advantage before my enemies could recuperate.
Ever played any of SSG's Warlords games? Best series ever IMO.