Cheapest priced copy (Battle for Zendikar): $0.35 at Card Kingdom, near mint, their price list as of .
Kalastria Healer 
Creature — Vampire Cleric Ally · 1/2 · Common · Battle for Zendikar · #114
Rally — Whenever this creature or another Ally you control enters, each opponent loses 1 life and you gain 1 life.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Battle for Zendikar | 114 | Common | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 25 August 2015If a creature with a rally ability enters the battlefield under your control at the same time as other Allies, that ability will trigger once for each of those creatures and once for the creature with the ability itself.
- 25 August 2015When an Ally enters the battlefield under your control, each rally ability of the permanents you control will trigger. You can put them on the stack in any order. The last ability you put on the stack will be the first one to resolve.