Aether Barrier

Whenever a player casts a creature spell, that player sacrifices a permanent unless they pay {1}.

Island

Arcane Signet

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

Mana Vault

Mana Vault doesn't untap during your untap step.
At the beginning of your upkeep, you may pay {4}. If you do, untap Mana Vault.
At the beginning of your draw step, if Mana Vault is tapped, it deals 1 damage to you.
{T}: Add {C}{C}{C}.

Sol Ring

Rising Waters

Lands don't untap during their controllers' untap steps.
At the beginning of each player's upkeep, that player untaps a land they control.

Tolaria

{T}: Add {U}.
{T}: Target creature loses banding and all "bands with other" abilities until end of turn. Activate only during any upkeep step.

Llawan, Cephalid Empress

When Llawan, Cephalid Empress enters the battlefield, return all blue creatures your opponents control to their owners' hands.
Your opponents can't cast blue creature spells.