Cheapest priced copy (Stronghold): $0.35 at Card Kingdom, near mint, their price list as of .
Temper 
Instant · Uncommon · Stronghold · #20
Prevent the next X damage that would be dealt to target creature this turn. For each 1 damage prevented this way, put a +1/+1 counter on that creature.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
1 printing · $0.35 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Stronghold | 20 | Uncommon | $0.35 | — |
2 rulings from Wizards of the Coast
- 4 October 2004You can make X be larger than the amount of damage, but you only get one counter for each actual point of damage prevented.
- 4 October 2004The +1/+1 counters do show up at the same time as any unprevented damage, which means they are there before you check for lethal damage.