Arcane Signet

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

Rakdos Signet

Smoldering Marsh

({T}: Add {B} or {R}.)
Smoldering Marsh enters the battlefield tapped unless you control two or more basic lands.

Falthis, Shadowcat Familiar

Commanders you control have menace and deathtouch.
Partner (You can have two commanders if both have partner.)

Command Tower

Sol Ring

Dragonskull Summit

Dragonskull Summit enters the battlefield tapped unless you control a Swamp or a Mountain.
{T}: Add {B} or {R}.

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Toggo, Goblin Weaponsmith

Landfall — Whenever a land enters the battlefield under your control, create a colorless Equipment artifact token named Rock with "Equipped creature has '{1}, {T}, Sacrifice Rock: This creature deals 2 damage to any target'" and equip {1}.
Partner (You can have two commanders if both have partner.)