Phyrexian Altar

Sacrifice a creature: Add one mana of any color.

Arcane Signet

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

Sol Ring

Rakdos, Lord of Riots

You can't cast Rakdos unless an opponent lost life this turn.
Flying, trample
Creature spells you cast cost {1} less to cast for each 1 life your opponents have lost this turn.

Command Tower

Mayhem Devil

Whenever a player sacrifices a permanent, this creature deals 1 damage to any target.

Jagged Barrens

This land enters tapped.
When this land enters, it deals 1 damage to target opponent.
{T}: Add {B} or {R}.

Rakdos Carnarium

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {B}{R}.

Judith, the Scourge Diva

Other creatures you control get +1/+0.
Whenever a nontoken creature you control dies, Judith deals 1 damage to any target.