This biome can be found on the surface of Geode in Uber-8 (PR 5000, no Light required), Uber-9 (PR 10000, 100 light) and Uber-10 (PR 15000, 2125 Light).
Each occurrence of Eerie Vale contains one Leviathan Lair. Type of Leviathan in the lair depends on an Uber its located in. Lobstroso spawns in Uber-8, Timmense, The Powerful Pontoon in Uber 9 and Ifera, Underlord of The Deep in Uber-10.
Defeat Leviathans to obtain Lesser Geodian Topside Cache, special Torches that provide Light stat and for an additional chance to drop Crystal-3 equipment.