Cheapest priced copy (Kaldheim): $0.35 at Card Kingdom, near mint, their price list as of .
Thornmantle Striker 
Creature — Elf Rogue · 4/3 · Uncommon · Kaldheim · #387
When this creature enters, choose one —
• Remove X counters from target permanent, where X is the number of Elves you control.
• Target creature an opponent controls gets -X/-X until end of turn, where X is the number of Elves you control.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Kaldheim | 387 | Uncommon | $0.35 | — |
3 rulings from Wizards of the Coast
- 5 February 2021For the first mode, you choose which counters are removed as the ability resolves. If the permanent has fewer counters on it than the number of Elves you control, you’ll remove all of them.
- 5 February 2021A planeswalker with no loyalty counters on it is put into its owner’s graveyard.
- 5 February 2021For each mode, use the number of Elves you control as the enters-the-battlefield ability resolves, including Thornmantle Striker itself if it’s still under your control.