Cheapest priced copy (Tales of Middle-earth Commander): $0.69 at Card Kingdom, near mint, their price list as of .
Selfless Squire 
Creature — Human Soldier · 1/1 · Rare · Murders at Karlov Manor Commander · #82
Flash
When this creature enters, prevent all damage that would be dealt to you this turn.
Whenever damage that would be dealt to you is prevented, put that many +1/+1 counters on this creature.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
4 printings · $0.69 to $1.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2016 | 4 | Rare | $1.49 | — |
| Commander 2021 | 103 | Rare | $0.79 | — |
| Tales of Middle-earth Commander | 176 | Rare | $0.69 | — |
| Murders at Karlov Manor Commander | 82 | Rare | $0.99 | — |
2 rulings from Wizards of the Coast
- 8 November 2016Selfless Squire's first triggered ability prevents all damage that would be dealt to you this turn after the triggered ability resolves, even if Selfless Squire leaves the battlefield.
- 8 November 2016Selfless Squire's second triggered ability doesn't trigger only when damage is prevented by its first triggered ability's effect. Any effect that uses the word "prevent" will cause it to trigger.