Cheapest priced copy (Commander 2019): $0.35 at Card Kingdom, near mint, their price list as of .
Skinthinner 
Creature — Zombie · 2/1 · Common · Legions · #80
Morph {3}{B}{B} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When this creature is turned face up, destroy target nonblack creature. It can't be regenerated.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
3 printings · $0.35 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2019 | 129 | Common | $0.35 | — |
| Legions | 80 | Common | $0.35 | $0.79 |
| The List | LGN-80 | Common | $0.35 | — |
One ruling from Wizards of the Coast
- 4 October 2004The trigger occurs when you use the Morph ability to turn the card face up, or when an effect turns it face up. It will not trigger on being revealed or on leaving the battlefield.