Cheapest priced copy (Strixhaven: School of Mages): $0.35 at Card Kingdom, near mint, their price list as of .
Maelstrom Muse 
Creature — Djinn Wizard · 2/4 · Uncommon · Strixhaven: School of Mages · #202
Flying
Whenever this creature attacks, the next instant or sorcery spell you cast this turn costs {X} less to cast, where X is this creature's power as this ability resolves.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Strixhaven: School of Mages | 202 | Uncommon | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 16 April 2021To determine the total cost of a spell, start with the mana cost or alternative cost you’re paying, add any cost increases, then apply any cost reductions (such as that of Maelstrom Muse’s triggered ability). The mana value of the spell is determined only by its mana cost, no matter what the total cost to cast the spell was.
- 16 April 2021Maelstrom Muse’s cost reduction can reduce only generic mana in a spell’s total cost. It can’t reduce colored mana requirements.