Battle Myrsphere is a rare Artifact Creature — Phyrexian Myr card from Unknown Event (UNK), collector number RA07a. Current market price: $66.69, TCGplayer market prices via Scryfall.
When Battle Myrsphere enters the battlefield, reveal cards from the top of your library until you reveal a battle card. Put it onto the battlefield, and the rest on the bottom of your library in a random order. Whenever Battle Myrsphere attacks, you may tap X untapped battles you control (so they're oriented like a regular Magic card). If you do, Battle Myrsphere gets +X/+0 until end of turn and deals X damage to the player or permanent.