Mini-Me

Wear the Moon Lord Mask, Torso and Legs together - a scavenger hunt across the secret seeds. The Mask drops from the Moon Lord himself (Champion of Terraria); the Torso comes from Golden Lock Boxes opened on a For the Worthy world; the Legs turn up in chests on drunk world or getfixedboi seeds (about 1-in-15 per chest). A single getfixedboi world - which layers all the seed effects - is the efficient hunting ground. Equip all three: cosplay of cosmic horror, achievement popped.