Tarrasque

The Tarrasque is a pure engine of fucking destruction. Dreaded by adventurers for its high hp value and its obscenely high regeneration ability, it is known to rampage across nations eating everything. It cannot fully be killed through normal means; therefore, A player (or group) lucky enough to reduce a Tarrasque to negative 10 hp will then have to use a wish or miracle spell to completely destroy it, with only a 50% chance of success. if unsuccessful it will wake up again x years later and fuck more shit up.