Fellwar Stone

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

Dark Ritual

Arcane Signet

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

Thought Vessel

You have no maximum hand size.
{T}: Add {C}.

Sol Ring

Mind Stone

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

Tergrid's Lantern

{T}: Target player loses 3 life unless they sacrifice a nonland permanent of their choice or discard a card.
{3}{B}: Untap Tergrid's Lantern.

Tergrid, God of Fright

Menace
Whenever an opponent sacrifices a nontoken permanent or discards a permanent card, you may put that card from a graveyard onto the battlefield under your control.