Cheapest priced copy (Eldritch Moon): $0.35 at Card Kingdom, near mint, their price list as of .
Somberwald Stag 
Creature — Elk · 4/3 · Uncommon · Jumpstart · #431
When this creature enters, you may have it fight target creature you don't control.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Eldritch Moon | 169 | Uncommon | $0.35 | $0.49 |
| Jumpstart | 431 | Uncommon | $0.35 | — |
2 rulings from Wizards of the Coast
- 13 July 2016If the targeted creature is an illegal target when Somberwald Stag’s ability tries to resolve, the ability doesn’t resolve. If Somberwald Stag is no longer on the battlefield, the targeted creature won’t deal or be dealt damage.
- 13 July 2016You choose the target of the triggered ability as it goes on the stack, but you choose whether or not to fight as that ability resolves.