Sword Coast Serpent can't be blocked as long as you've cast a noncreature spell this turn.
Capsizing Wave 1U
Instant — Adventure
Return target creature to its owner's hand. (Then exile this card. You may cast the creature later from exile.)
Non Foil / Near Mint - $0.56
Non Foil / Slightly Played - $0.50
Non Foil / Moderately Played - $0.45
Non Foil / Heavily Played - $0.34
Non Foil / Damaged - $0.28