Cheapest priced copy (Secrets of Strixhaven Commander): $0.99 at Card Kingdom, near mint, their price list as of .
Magma Opus 
Instant · Mythic · Strixhaven: School of Mages · #203
Magma Opus deals 4 damage divided as you choose among any number of targets. Tap two target permanents. Create a 4/4 blue and red Elemental creature token. Draw two cards.
{U/R}{U/R}, Discard this card: Create a Treasure token.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
6 printings · $0.99 to $5.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Strixhaven: School of Mages Promos | 203p | Mythic | $1.49 | $2.99 |
| Strixhaven: School of Mages Promos | 203s | Mythic | — | $2.79 |
| Secrets of Strixhaven Commander | 318 | Mythic | $0.99 | — |
| Strixhaven: School of Mages | 203 | Mythic | $0.99 | $2.49 |
| Strixhaven: School of Mages | 346 | Mythic | $2.99 | $5.99 |
| Tarkir: Dragonstorm Commander | 296 | Mythic | $0.99 | — |
5 rulings from Wizards of the Coast
- 16 April 2021You choose all targets for Magma Opus as you cast the spell. This includes up to four targets for the first effect and two target permanents for the second effect.
- 16 April 2021If somehow all of Magma Opus's targets are illegal as it tries to resolve, none of its effects happen. You will not create an Elemental token or draw two cards.
- 16 April 2021You must choose two different target permanents for the second effect. You may choose permanents that are already tapped.
- 16 April 2021The same permanent can be chosen as a target for each of the two instances of "target." That is, you can have Magma Opus both deal damage to a creature or planeswalker and then tap it. (We're having a hard time imagining why you would, but you're the brilliant student.)
- 16 April 2021You also choose how the 4 damage will be divided among the first group of targets as you cast Magma Opus. You must have at least 1 damage dealt to each of those targets.