If you have a class like Eternal Inversionist, which can target 6 enemies at once, complete Syrrus' "Free the Moglins" quest at /icepike by defeating Frozen Moglins. Otherwise, complete Syrrus' "Thin the Horde (Farming Quest)". The enemies you need to farm are near the end of the map.
Also make sure to enable Quest Log Turn-Ins and Reaccept Quest After Turn-In from Advanced Options. This way you can keep your Quest Log open and turn in quests from there. You can access your Quest Log by pressing L.