Sahagin is a common Creature — Merfolk Warrior card from Final Fantasy (FIN), collector number 71. Current market price: $0.15 (foil $0.19), TCGplayer market prices via Scryfall.
Whenever you cast a noncreature spell, if at least four mana was spent to cast it, put a +1/+1 counter on this creature and it can't be blocked this turn.