Cheapest priced copy (Core Set 2019): $1.29 at Card Kingdom, near mint, their price list as of .
Serra's Guardian 
Creature — Angel · 5/5 · Rare · Core Set 2019 · #284
Flying (This creature can't be blocked except by creatures with flying or reach.)
Vigilance (Attacking doesn't cause this creature to tap.)
Other creatures you control have vigilance.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $1.29 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Core Set 2019 | 284 | Rare | $1.29 | — |
| Core Set 2020 | 310 | Rare | $1.29 | — |
One ruling from Wizards of the Coast
- 12 July 2019A creature losing vigilance after it has attacked (most likely because Serra’s Guardian leaves the battlefield) won’t cause it to become tapped.