Island

Arcane Signet

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

Mountain

Rakdos Signet

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Terramorphic Expanse

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Command Tower

Swamp

Izzet Signet

Evolving Wilds

Barad-dûr

Barad-dûr enters tapped unless you control a legendary creature.
{T}: Add {B}.
{X}{X}{B}, {T}: Amass Orcs X. Activate only if a creature died this turn.

Dimir Signet

Sauron, the Dark Lord

Ward—Sacrifice a legendary artifact or legendary creature.
Whenever an opponent casts a spell, amass Orcs 1.
Whenever an Army you control deals combat damage to a player, the Ring tempts you.
Whenever the Ring tempts you, you may discard your hand. If you do, draw four cards.