Death Seeker appears through the second section of the Tziah Block within Tartarus, in groups of 3 or alongside Liberating Idols. They will typically attack physically or use Maragion, but they will also use their Darkness skills randomly.
Death Seekers may later be found in the second and third section of Antenora within the Abyss of Time, where they now use the Evil Smile and Mudoon skills.
Death Seekers appear on floors 1 through 4 of Marukyu Striptease within the Midnight Channel. In battle they will simply alternate between casting Zionga or casting Mind Charge followed by Zionga. Upon being defeated, they may drop the Iron Eyeball material. Selling 6 Iron Eyeballs at Daidara will unlock the Gothic Sword weapon for the protagonist in the shop.
In the Golden, it may also drop Fluorite for trade at Shiroku Pub.