Cheapest priced copy (Innistrad): $0.35 at Card Kingdom, near mint, their price list as of .
Selfless Cathar 
Creature — Human Cleric · 1/1 · Common · Magic 2015 · #31
{1}{W}, Sacrifice this creature: Creatures you control get +1/+1 until end of turn.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Innistrad | 30 | Common | $0.35 | $0.49 |
| Magic 2015 | 31 | Common | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 22 September 2011Only creatures you control when Selfless Cathar's ability resolves will be affected. Creatures that enter or that you gain control of later in the turn will not.
- 22 September 2011You can activate Selfless Cathar's ability even if you control no other creatures.