7th Interportal Tournament of HMM3-OFF: "Earth Magic"

I didn't know that a single Gorgon could destroy a Rust Monster in 3 turns.

Not a Rust Monster in three turns, but three Rust Monsters in three turns. One Gorgon cannot destroy more than one unit. And in general, the maximum number of units that, in addition to direct damage, a stack of N Gorgons can destroy, is equal to [(N-1)/10+1], rounded down.