how to get to cave to capture epics?

So i read here on the forums about caves and such where you can catch epics like meniss. I've been grinding on volcano 10 veteran and i haven't seen any meniss (except for miniboss battle). how do you access this cave thing?

So i read here on the forums about caves and such where you can catch epics like meniss. I've been grinding on volcano 10 veteran and i haven't seen any meniss (except for miniboss battle). how do you access this cave thing?

hey, it is volcano 10 EXPERT, not VETERAN