Shu Yun, the Silent Tempest is a rare Legendary Creature — Human Monk card from The List (PLST), collector number FRF-52. Current market price: $0.19, TCGplayer market prices via Scryfall.
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.) Whenever you cast a noncreature spell, you may pay {R/W}{R/W}. If you do, target creature gains double strike until end of turn.