Cheapest priced copy (Dominaria): $0.35 at Card Kingdom, near mint, their price list as of .
Shield of the Realm 
Artifact — Equipment · Uncommon · Dominaria · #228
If a source would deal damage to equipped creature, prevent 2 of that damage.
Equip {1}
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dominaria | 228 | Uncommon | $0.35 | $0.49 |
3 rulings from Wizards of the Coast
- 27 April 2018If a creature is equipped with two Shields of the Realm, 4 damage will be prevented. Three Shields of the Realm will prevent 6 damage, and so on.
- 27 April 2018If multiple sources would deal damage to the equipped creature at once (for example, several blocking creatures), 2 damage from each of those sources is prevented.
- 27 April 2018If multiple replacement effects would modify how damage would be dealt, the controller of the permanent being dealt damage chooses the order in which to apply those effects.