The Mimic/Strategies - OSRS Wiki

Upon completion of an elite or master clue scroll, the casket received has a chance of turning out to be a mimic chest. Mimic caskets can only be obtained from an elite or master reward casket after asking the strange casket to enable the chance to obtain a mimic casket (which is disabled by default).

OSRS' Treasure Trails Update: Mimic Boss Changes, Beginner Scroll Clues, Stackable Caskets and More

Arcane spirit shield - OSRS Wiki

The Mimic - OSRS Wiki

Spindel - OSRS Wiki

Mimic Display - OSRS Wiki

Amulet of power - OSRS Wiki

Mimic Guide, Athensps Wiki

Void knight gloves - OSRS Wiki

Treasure Trails/Guide/Hot Cold - OSRS Wiki

Tormented bracelet - OSRS Wiki

Phantom Muspah - OSRS Wiki

Clue scroll (easy) - OSRS Wiki

Strange casket - OSRS Wiki

Radagon of the Golden Order

Grotesque Guardians - OSRS Wiki