I met Keeper with my party of 3 members - Fighter (made from ninja on lvl 18), bishop and mage. 1st turn - Element Shield and Soul Shield. 2 casts of Banish on the second turn cleared off his minions. Then I went closely to him (mage and bishop were too far from Keeper to reach) and during 2-3 turns wiped him out (my fighter has only the Fang
( ).