Cheapest priced copy (Lorwyn): $0.35 at Card Kingdom, near mint, their price list as of .
Wellgabber Apothecary 
Creature — Merfolk Cleric · 2/3 · Common · Lorwyn · #47
{1}{W}: Prevent all damage that would be dealt to target tapped Merfolk or Kithkin creature this turn.
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Lorwyn | 47 | Common | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 1 October 2007Once the ability has resolved, all damage that would be dealt to that creature for the rest of the turn will be prevented, regardless of whether it’s tapped or untapped at the time that damage would be dealt.
- 1 October 2007The targeted creature must be tapped when the ability is activated and when it resolves. It doesn’t need to remain tapped in between.