Mirrormind Crown is a rare Artifact — Equipment card from Lorwyn Eclipsed (ECL), collector number 381. Current market price: $1.34 (foil $2.02), TCGplayer market prices via Scryfall.
As long as this Equipment is attached to a creature, the first time you would create one or more tokens each turn, you may instead create that many tokens that are copies of equipped creature. Equip {2}