its entirely random where the cores are. they can be down inside big lairs or inside secret rooms or on corridors.

also 2x 2stars is EXTREMELY rare. so youre either insanely unlucky or it was just one 2 star and not 2.

also this isnt a BOSS DEN at all. its a regular dungeon like burials and crypts. these didnt have bosses or rewards for doing a FULL CLEAR either. so not sure what the thought process here is on why mistlands dungeons should be different all of a sudden.