You can't cast Bad Knight if you're on the Mirran team
it gains the following abilities until end of turn
Set: Sword & Shield: Black Star Promos Type: Fighting Rarity: Promo Retreat cost: Colorless
Set: XY: BREAKpoint Type: Colorless Rarity: Ultra Rare Retreat cost: Colorless
Set: HeartGold & SoulSilver: Triumphant Type: Grass Rarity: Ultra Rare Retreat cost: Colorless
Tricky Mage [Unknown Event] XY09 You can't cast Bad KnightSet: Unknown Event Type: Creature Human Wizard Rarity: Common Cost: {2}{U} When Tricky Mage enters the battlefield, if you're on the Mirran team, search your library for an artifact card with mana value 2 or less, reveal it, put it into your hand, then shuffle. If you're on the Phyrexian team, search your library for an artifact card with mana value 6 or greater, reveal it, and put it into your hand, then shuffle.