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).

Clue scroll (medium) - OSRS Wiki

Ethereal Mimic - OSRS Wiki

Nex - OSRS Wiki

Wintertodt - OSRS Wiki

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

Diamond dragon bolts (e) - OSRS Wiki

TzTok-Jad - OSRS Wiki

Can I do mimic? : r/2007scape

Void ranger helm - OSRS Wiki

TzKal-Zuk - OSRS Wiki

Treasure Trails/Full guide/Master - OSRS Wiki

Should I try for the mimic at this level, or just give up? : r/ironscape

Wintertodt - OSRS Wiki