While I'm making up spells, lol, I might as well include this one: A giant clam rises up from the battle circle, and opens to reveal a mermaid, whose song (made physical by music bars and notes) is what does the damage. I think the song doing damage part is particularly fitting because of that one poem about the sea captain having to block out the song of the mermaids that lures ships to crash on the rocks... I can't remember the name of it.