Lolth, Spider Queen

Whenever a creature you control dies, put a loyalty counter on Lolth, Spider Queen.
0: You draw a card and you lose 1 life.
−3: Create two 2/1 black Spider creature tokens with menace and reach.
−8: You get an emblem with "Whenever an opponent is dealt combat damage by one or more creatures you control, if that player lost less than 8 life this turn, they lose life equal to the difference."

Mitotic Slime

When Mitotic Slime dies, create two 2/2 green Ooze creature tokens. They have "When this creature dies, create two 1/1 green Ooze creature tokens."

Sprouting Thrinax

When Sprouting Thrinax dies, create three 1/1 green Saproling creature tokens.

Purphoros, God of the Forge

Indestructible
As long as your devotion to red is less than five, Purphoros isn't a creature.
Whenever another creature you control enters, Purphoros deals 2 damage to each opponent.
{2}{R}: Creatures you control get +1/+0 until end of turn.

Attrition

{B}, Sacrifice a creature: Destroy target nonblack creature.

Goblin Bombardment

Sacrifice a creature: Goblin Bombardment deals 1 damage to any target.

Skullmulcher

Devour 1 (As this enters, you may sacrifice any number of creatures. This creature enters with that many +1/+1 counters on it.)
When Skullmulcher enters, draw a card for each creature it devoured.

Second Harvest

For each token you control, create a token that's a copy of that permanent.

Impact Tremors

Whenever a creature you control enters, this enchantment deals 1 damage to each opponent.

Thorn-Thrash Viashino

Devour 2 (As this enters, you may sacrifice any number of creatures. This creature enters with twice that many +1/+1 counters on it.)
{G}: Thorn-Thrash Viashino gains trample until end of turn.

Parallel Lives

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.

Hellkite Hatchling

Devour 1 (As this enters, you may sacrifice any number of creatures. This creature enters with that many +1/+1 counters on it.)
Hellkite Hatchling has flying and trample if it devoured a creature.

Nether Traitor

Haste
Shadow (This creature can block or be blocked by only creatures with shadow.)
Whenever another creature is put into your graveyard from the battlefield, you may pay {B}. If you do, return Nether Traitor from your graveyard to the battlefield.

Golgari Signet

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Gruul Signet

Endless Cockroaches

When Endless Cockroaches dies, return it to its owner's hand.

Bloodsoaked Champion

Bloodsoaked Champion can't block.
Raid — {1}{B}: Return Bloodsoaked Champion from your graveyard to the battlefield. Activate only if you attacked this turn.

Rakdos Signet

Bloodspore Thrinax

Devour 1 (As this enters, you may sacrifice any number of creatures. This creature enters with that many +1/+1 counters on it.)
Each other creature you control enters with an additional X +1/+1 counters on it, where X is the number of +1/+1 counters on Bloodspore Thrinax.

Thantis, the Warweaver

Vigilance, reach
All creatures attack each combat if able.
Whenever a creature attacks you or a planeswalker you control, put a +1/+1 counter on Thantis, the Warweaver.

Elemental Bond

Whenever a creature you control with power 3 or greater enters, draw a card.

Cauldron of Souls

{T}: Choose any number of target creatures. Each of those creatures gains persist until end of turn. (When it dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Decree of Pain

Destroy all creatures. They can't be regenerated. Draw a card for each creature destroyed this way.
Cycling {3}{B}{B} ({3}{B}{B}, Discard this card: Draw a card.)
When you cycle Decree of Pain, all creatures get -2/-2 until end of turn.

Spider Spawning

Create a 1/2 green Spider creature token with reach for each creature card in your graveyard.
Flashback {6}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Sol Ring

Dictate of Erebos

Flash
Whenever a creature you control dies, each opponent sacrifices a creature of their choice.

Reassembling Skeleton

{1}{B}: Return this card from your graveyard to the battlefield tapped.

Anger

Haste
As long as Anger is in your graveyard and you control a Mountain, creatures you control have haste.