Cheapest priced copy (Commander 2016): $0.49 at Card Kingdom, near mint, their price list as of .
Wild Beastmaster 
Creature — Human Shaman · 1/1 · Rare · Return to Ravnica · #139
Whenever this creature attacks, each other creature you control gets +X/+X until end of turn, where X is this creature's power.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.49 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2016 | 176 | Rare | $0.49 | — |
| Midnight Hunt Commander | 146 | Rare | $0.49 | — |
| Return to Ravnica | 139 | Rare | $0.49 | $1.99 |
2 rulings from Wizards of the Coast
- 1 October 2012The value of X is determined when the triggered ability resolves. If Wild Beastmaster is no longer on the battlefield at that time, use its last known power to determine the value of X.
- 14 July 2017If this creature's power is negative as its ability resolves, X is considered to be 0.