The Amulet of Kings

{t}: Add one mana of any color to your mana
pool. Activate this ability only if you control
another nonland legendary permanent.
{t}, Exile The Amulet of Kings: Target legendary
permanent you control gains protection from
the color of your choice until end of turn.
"The Amulet of Kings. It is the Empire's sacred
emblem of rulership. It must pass to the last of the
Dragon's Blood." ~ Uriel Septim VII