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).

The Mimic - OSRS Wiki

Nex - OSRS Wiki

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Spindel - OSRS Wiki

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Wintertodt - OSRS Wiki

Magus ring - OSRS Wiki

Ring of the gods (i) - OSRS Wiki