Cheapest priced copy (Foundations Jumpstart): $0.35 at Card Kingdom, near mint, their price list as of .
Warbriar Blessing 
Enchantment — Aura · Common · Theros Beyond Death · #204
Enchant creature you control
When this Aura enters, enchanted creature fights up to one target creature you don't control. (Each deals damage equal to its power to the other.)
Enchanted creature gets +0/+2.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
4 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Foundations Jumpstart | 739 | Common | $0.35 | — |
| The List | THB-204 | Common | $0.35 | — |
| Theros Beyond Death | 204 | Common | $0.35 | $0.49 |
| Wilds of Eldraine Commander | 137 | Common | $0.35 | — |
2 rulings from Wizards of the Coast
- 24 January 2020If Warbriar Blessing leaves the battlefield before its enters-the-battlefield triggered ability resolves, the creature it last enchanted before it left will be the one to fight.
- 24 January 2020If the target creature is an illegal target when Warbriar Blessing's triggered ability tries to resolve, the ability doesn't resolve. If the enchanted creature is no longer on the battlefield, the target creature won't deal or be dealt damage.