Play under the casual difficulty setting and train your chimera to level 15, and increase the "Summon Chimera" skill to ten. Enable respawning enemies to have them appear again at cleared locations. Go to the entrance of Cold Caverns and kill all enemies, besides the Grubshriek Hives. Stand there, with disabled Katarina while your chimera kills Grubshrieks. Note: You may have to re-summon it as needed.