Pir, Imaginative Rascal

Partner with Toothy, Imaginary Friend (When this creature enters, target player may put Toothy into their hand from their library, then shuffle.)
If one or more counters would be put on a permanent your team controls, that many plus one of each of those kinds of counters are put on that permanent instead.

All-Seeing Arbiter

Flying
Whenever this creature enters or attacks, draw two cards, then discard a card.
Whenever you discard a card, target creature an opponent controls gets -X/-0 until your next turn, where X is the number of different mana values among cards in your graveyard.

Pack Rat

Pack Rat's power and toughness are each equal to the number of Rats you control.
{2}{B}, Discard a card: Create a token that's a copy of this creature.

Lazotep Chancellor

Whenever you discard a card, you may pay {1}. If you do, amass Zombies 2. (Put two +1/+1 counters on an Army you control. It's also a Zombie. If you don't control an Army, create a 0/0 black Zombie Army creature token first.)

Feast of Sanity

Whenever you discard a card, this enchantment deals 1 damage to any target and you gain 1 life.

Ominous Seas

Whenever you draw a card, put a foreshadow counter on this enchantment.
Remove eight foreshadow counters from this enchantment: Create an 8/8 blue Kraken creature token.
Cycling {2} ({2}, Discard this card: Draw a card.)

Chasm Skulker

Whenever you draw a card, put a +1/+1 counter on this creature.
When this creature dies, create X 1/1 blue Squid creature tokens with islandwalk, where X is the number of +1/+1 counters on this creature. (They can't be blocked as long as defending player controls an Island.)

Dying to Serve

Whenever you discard one or more cards, create a tapped 2/2 black Zombie creature token. This ability triggers only once each turn.

Wild Mongrel

Discard a card: This creature gets +1/+1 and becomes the color of your choice until end of turn.

Junk Golem

This creature enters with three +1/+1 counters on it.
At the beginning of your upkeep, sacrifice this creature unless you remove a +1/+1 counter from it.
{1}, Discard a card: Put a +1/+1 counter on this creature.

Skirge Familiar

Ayula's Influence

Discard a land card: Create a 2/2 green Bear creature token.

Mindless Automaton

This creature enters with two +1/+1 counters on it.
{1}, Discard a card: Put a +1/+1 counter on this creature.
Remove two +1/+1 counters from this creature: Draw a card.

Toothy, Imaginary Friend

Partner with Pir, Imaginative Rascal (When this creature enters, target player may put Pir into their hand from their library, then shuffle.)
Whenever you draw a card, put a +1/+1 counter on Toothy.
When Toothy leaves the battlefield, draw a card for each +1/+1 counter on it.

Diamond Lion

{T}, Discard your hand, Sacrifice this creature: Add three mana of any one color. Activate only as an instant.

Awaken the Erstwhile

Each player discards all the cards in their hand, then creates that many 2/2 black Zombie creature tokens.

Bone Miser

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

Teferi, Temporal Pilgrim

Whenever you draw a card, put a loyalty counter on Teferi.
0: Draw a card.
−2: Create a 2/2 blue Spirit creature token with vigilance and "Whenever you draw a card, put a +1/+1 counter on this token."
−12: Target opponent chooses a permanent they control and returns it to its owner's hand. Then they shuffle each nonland permanent they control into its owner's library.

Noose Constrictor

Reach
Discard a card: This creature gets +1/+1 until end of turn.

Lotleth Troll

Trample
Discard a creature card: Put a +1/+1 counter on this creature.
{B}: Regenerate this creature.

Hell Mongrel

Discard a card: This creature gets +1/+1 until end of turn.
Madness {2}{B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Damia, Sage of Stone

Deathtouch
Skip your draw step.
At the beginning of your upkeep, if you have fewer than seven cards in hand, draw cards equal to the difference.

Oneirophage

Flying
Whenever you draw a card, put a +1/+1 counter on this creature.

Jace's Projection

Whenever you draw a card, put a +1/+1 counter on this creature.
{3}{U}: Put a loyalty counter on target Jace planeswalker.