Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Sauron, Lord of the Rings

When you cast this spell, amass Orcs 5, mill five cards, then return a creature card from your graveyard to the battlefield.
Trample
Whenever a commander an opponent controls dies, the Ring tempts you.

Sol Ring

Prince of Thralls

Whenever a permanent an opponent controls is put into a graveyard, put that card onto the battlefield under your control unless that opponent pays 3 life.

Demon's Herald

{2}{B}, {T}, Sacrifice a blue creature, a black creature, and a red creature: Search your library for a card named Prince of Thralls, put it onto the battlefield, then shuffle.