Megrim

Whenever an opponent discards a card, this enchantment deals 2 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.

Teferi's Puzzle Box

At the beginning of each player's draw step, that player puts the cards in their hand on the bottom of their library in any order, then draws that many cards.

The Rollercrusher Ride

Delirium — If a source you control would deal noncombat damage to a permanent or player while there are four or more card types among cards in your graveyard, it deals double that damage instead.
When The Rollercrusher Ride enters, it deals X damage to each of up to X target creatures.

Kederekt Parasite

Whenever an opponent draws a card, if you control a red permanent, you may have this creature deal 1 damage to that player.

Magus of the Wheel

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

Howling Mine

At the beginning of each player's draw step, if this artifact is untapped, that player draws an additional card.

Psychosis Crawler

Psychosis Crawler's power and toughness are each equal to the number of cards in your hand.
Whenever you draw a card, each opponent loses 1 life.

Gnat Miser

Each opponent's maximum hand size is reduced by one.

Syr Konrad, the Grim

Whenever another creature dies, or a creature card is put into a graveyard from anywhere other than the battlefield, or a creature card leaves your graveyard, Syr Konrad deals 1 damage to each opponent.
{1}{B}: Each player mills a card. (They each put the top card of their library into their graveyard.)

Thought Vessel

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

Underworld Dreams

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

Deathrite Shaman

{T}: Exile target land card from a graveyard. Add one mana of any color.
{B}, {T}: Exile target instant or sorcery card from a graveyard. Each opponent loses 2 life.
{G}, {T}: Exile target creature card from a graveyard. You gain 2 life.

Geier Reach Sanitarium

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

Stormfist Crusader

Menace
At the beginning of your upkeep, each player draws a card and loses 1 life.

Font of Mythos

At the beginning of each player's draw step, that player draws two additional cards.

Fate Unraveler

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

Orcish Bowmasters

Flash
When this creature enters and whenever an opponent draws a card except the first one they draw in each of their draw steps, this creature deals 1 damage to any target. Then amass Orcs 1.

Gixian Puppeteer

Whenever you draw your second card each turn, each opponent loses 2 life and you gain 2 life.
When this creature dies, return another target creature card with mana value 3 or less from your graveyard to the battlefield.

Master of the Feast

Flying
At the beginning of your upkeep, each opponent draws a card.

Sheoldred, the Apocalypse

Deathtouch
Whenever you draw a card, you gain 2 life.
Whenever an opponent draws a card, they lose 2 life.

Leela, Sevateem Warrior

Whenever an opponent draws a card except the first one they draw in each of their draw steps, put a +1/+1 counter on Leela.
Doctor's companion (You can have two commanders if the other is the Doctor.)

Waste Not

Whenever an opponent discards a creature card, create a 2/2 black Zombie creature token.
Whenever an opponent discards a land card, add {B}{B}.
Whenever an opponent discards a noncreature, nonland card, draw a card.

Winter, Misanthropic Guide

Ward {2}
At the beginning of your upkeep, each player draws two cards.
Delirium — As long as there are four or more card types among cards in your graveyard, each opponent's maximum hand size is equal to seven minus the number of those card types.

Sol Ring

Dark Deal

Each player discards all the cards in their hand, then draws that many cards minus one.

Geth's Grimoire

Whenever an opponent discards a card, you may draw a card.

Scrawling Crawler

At the beginning of your upkeep, each player draws a card.
Whenever an opponent draws a card, that player loses 1 life.

Spiteful Visions

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

Bloodchief Ascension

At the beginning of each end step, if an opponent lost 2 or more life this turn, you may put a quest counter on this enchantment. (Damage causes loss of life.)
Whenever a card is put into an opponent's graveyard from anywhere, if this enchantment has three or more quest counters on it, you may have that player lose 2 life. If you do, you gain 2 life.

Razorkin Needlehead

This creature has first strike during your turn.
Whenever an opponent draws a card, this creature deals 1 damage to them.