Target of Mission Two: Seething Revenants

Once you have unlocked the Sons of Hodir daily quests, you can go to Dun Niffelem to pick up the quest Hot and Cold from Fjorn Anvil. Upon completion, you will get an extra 13g23s at level 80. Because the daily quest, Hot and Cold, has you going to both locations, and because the area can be highly farmed at certain parts of the day, you might do better to do a circuit through the two adjacent areas.

Brittle Revenants are icy, and will drop everything that their fiery cousins drop, with the substitution of Crystallized Earth for Crystallized Fire. Earth is not in high demand, because it drops readily for miners, but depending on your profession, you could use them to make Mesos. For example, Tailors can use it to craft blue PvP cloth gear, certain high-end, profitable epic jewelry take six Eternal Earths, and Enchant Gloves Armsman and Enchant Shield - Defense use up an awful lot, and sell well.