I thought of this during a bombring event.
Basically, in a small map, a GIGANTIC bombring, with an absolutely OBSCENE amount of health, will spawn. After about 15-30 seconds, it'll exploding, wiping out everyone in the arena. But if everyone can kill it before it can finish its uninterruptable cast, then everyone that did damage to it(so as to avoid people AFKing in the arena) with get some Muh Coins for their efforts. But if it blows up, then hey, it was a fun little challenge.