Team Mage is a uncommon Creature — Human Wizard card from Unknown Event (UNK), collector number UU03a.
When Team Mage enters, search you library for an artifact card with mana value 4 or greater if you're on Team Cloudspire or an artifact card with mana value 3 or less if you're on Team Speed Demons. Reveal that card, put it into your hand, then shuffle.