Cheapest priced copy (Tarkir: Dragonstorm Commander): $6.99 at Card Kingdom, near mint, their price list as of .
Will of the Mardu 
Instant · Rare · Tarkir: Dragonstorm Commander · #17
Choose one. If you control a commander as you cast this spell, you may choose both instead.
• Create a number of 1/1 red Warrior creature tokens equal to the number of creatures target player controls.
• Will of the Mardu deals damage to target creature equal to the number of creatures you control.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
2 printings · $6.99 to $7.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Tarkir: Dragonstorm Commander | 17 | Rare | $6.99 | — |
| Tarkir: Dragonstorm Commander | 57 | Rare | $7.49 | — |
3 rulings from Wizards of the Coast
- 4 April 2025Once you’ve announced that you’re casting this spell, players can’t take any actions until you’ve finished doing so. Notably, opponents can’t try to remove your commander to change how many modes you may choose.
- 4 April 2025Whether or not you control a commander is determined only once, as you choose the modes for this spell. If you somehow lose control of that commander before you finish casting the spell (perhaps because you sacrifice it to activate a mana ability), it won’t change the number of modes chosen.
- 4 April 2025The commander you control doesn’t have to be your commander.