Mirrormind Crown is a rare Artifact — Equipment card from Lorwyn Eclipsed Promos (PECL), collector number 258p. Current market price: $0.68 (foil $1.31), 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}