First of all you need to take and pass all quests from NPC Rafforty. Then you should obtain from mobs in Frozen Labyrinth Sylver Hemocytes and collect them. After this you have to gather a party, and to give each member 10 Sylver Hemocytes. Then you need to find NPC near the bridge near The Ice Queen's Castle, party leader have to talk to him and then teleport to the castle with his party. You'll have only 35 minutes to kill all moms and boss.