Cheapest priced copy (Final Fantasy): $0.35 at Card Kingdom, near mint, their price list as of .
Sahagin 
Creature — Merfolk Warrior · 1/3 · Common · Final Fantasy · #71
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.
Legal inCommanderBrawlStandardPioneerModernLegacyVintagePauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Final Fantasy | 71 | Common | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 6 June 2025Once Sahagin has been blocked, casting a noncreature spell in order to cause Sahagin's ability to trigger won't cause Sahagin to become unblocked.
- 6 June 2025Sahagin's ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered or otherwise leaves the stack.