Magus of the Wheel

{1}{R}, {T}, Sacrifice this creature: Each player discards their hand, then draws seven cards.

Megrim

Whenever an opponent discards a card, this enchantment deals 2 damage to that player.

Fate Unraveler

Whenever an opponent draws a card, this creature deals 1 damage to that player.

Ob Nixilis, the Hate-Twisted

Whenever an opponent draws a card, Ob Nixilis deals 1 damage to that player.
−2: Destroy target creature. Its controller draws two cards.

Terminate

Destroy target creature. It can't be regenerated.

Decanter of Endless Water

You have no maximum hand size.
{T}: Add one mana of any color.

Chaos Warp

The owner of target permanent shuffles it into their library, then reveals the top card of their library. If it's a permanent card, they put it onto the battlefield.

Exotic Orchard

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

Geier Reach Sanitarium

{T}: Add {C}.
{2}, {T}: Each player draws a card, then discards a card.

Arcane Signet

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

Island

Nekusar, the Mindrazer

At the beginning of each player's draw step, that player draws an additional card.
Whenever an opponent draws a card, Nekusar deals 1 damage to that player.

Swamp

Command Tower

Underworld Dreams

Whenever an opponent draws a card, this enchantment deals 1 damage to that player.

Mountain

Elder Brain

Menace
Whenever this creature attacks a player, exile all cards from that player's hand, then they draw that many cards. You may play lands and cast spells from among the exiled cards for as long as they remain exiled. If you cast a spell this way, you may spend mana as though it were mana of any color to cast it.