They do get a huge boost in levels every time you defeat them. Beris, you will want the Demon Layer weapon. I usually use Overpower (Power buff), Detect weakness (Crit chance buff), and overlimit (massive 1-turn dmg increase) before smacking her with a strong attack. Ushris (Thick-thighed witch) can be gotten rid of only one time by holy headpats. Second time onwards, seduction attacks get through her barrier. If you seek levels, fight mimics. Mimics are easy prey for seduction-based attacks and drop lots of exp and eros (money).