Obsidemon's Hypogeum Key

 is a key.

Obtaining

 * Crafted by a Handyman (Lv. 100) from
 * 5 Atomystique Stone
 * 5 Aspen
 * 5 Solftara Residue
 * 4 Woolly Bow Meow Hair
 * 4 Stunted Rat Fabric
 * 4 Gullipop Feather
 * 5 Steam Crackler Heart
 * 5 Obsidian