Cheapest priced copy (Modern Horizons): $0.35 at Card Kingdom, near mint, their price list as of .
Martyr's Soul 
Creature — Spirit Soldier · 3/2 · Common · Jumpstart 2022 · #212
Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
When this creature enters, if you control no tapped lands, put two +1/+1 counters on it.
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
2 printings · $0.35 to $1.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Jumpstart 2022 | 212 | Common | $0.49 | — |
| Modern Horizons | 19 | Common | $0.35 | $1.49Out of stock |
7 rulings from Wizards of the Coast
- 14 June 2019If you control any tapped lands as Martyr's Soul enters the battlefield, its last ability doesn't trigger at all. If you control any tapped lands as the ability resolves, you won't put two +1/+1 counters on Martyr's Soul.
- 12 January 2024Because convoke isn't an alternative cost, it can be used in conjunction with alternative costs.
- 12 January 2024If a creature you control has a mana ability with {T} in the cost, activating that ability while casting a spell with convoke will result in the creature being tapped before you pay the spell's costs. You won't be able to tap it again for convoke. Similarly, if you sacrifice a creature to activate a mana ability while casting a spell with convoke, that creature won't be on the battlefield when you pay the spell's costs, so you won't be able to tap it for convoke.
- 12 January 2024Tapping a multicolored creature using convoke will pay for {1} or one mana of your choice of any of that creature's colors.
- 12 January 2024You can tap any untapped creature you control to convoke a spell, even one you haven't controlled continuously since the beginning of your most recent turn.
- 12 January 2024When calculating a spell's total cost, include any alternative costs, additional costs, or anything else that increases or reduces the cost to cast the spell. Convoke applies after the total cost is calculated. Convoke doesn't change a spell's mana cost or mana value.
- 12 January 2024Tapping an untapped creature that's attacking or blocking to convoke a spell won't cause that creature to stop attacking or blocking.