Cheapest priced copy (Invasion): $0.35 at Card Kingdom, near mint, their price list as of .
Pledge of Loyalty 
Enchantment — Aura · Uncommon · Invasion · #24
Enchant creature
Enchanted creature has protection from each color among permanents you control. This effect doesn't remove this Aura.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper