Cheapest priced copy (Foundations Jumpstart): $0.35 at Card Kingdom, near mint, their price list as of .
Steadfast Sentry 
Creature — Human Soldier · 3/2 · Common · Foundations Jumpstart · #262
Vigilance (Attacking doesn't cause this creature to tap.)
When this creature dies, put a +1/+1 counter on target creature you control.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Foundations Jumpstart | 262 | Common | $0.35 | — |
| Core Set 2020 | 40 | Common | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 12 July 2019If another creature is dealt lethal damage at the same time as Steadfast Sentry, Steadfast Sentry's triggered ability can't put a +1/+1 counter on the other creature in time to save it.