Fellwar Stone

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

Plague Reaver

At the beginning of your end step, sacrifice each other creature you control.
Discard two cards, Sacrifice Plague Reaver: Choose target opponent. Return Plague Reaver to the battlefield under that player's control at the beginning of their next upkeep.

Arcane Signet

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

Rakdos Signet

Ramunap Excavator

Patriar's Seal

{T}: Add one mana of any color.
{1}, {T}: Untap target legendary creature you control.

Sol Ring

Eater of Days

Flying, trample
When Eater of Days enters the battlefield, you skip your next two turns.

Golgari Signet

Gruul Signet

The Beamtown Bullies

Vigilance, haste
{T}: Target opponent whose turn it is puts target nonlegendary creature card from your graveyard onto the battlefield under their control. It gains haste. Goad it. At the beginning of the next end step, exile it. (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)