Writhing Necromass

This spell costs {1} less to cast for each creature card in your graveyard.
Deathtouch

Woodland Chasm

({T}: Add {B} or {G}.)
Woodland Chasm enters tapped.

Generous Ent

Reach
When Generous Ent enters, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")
Forestcycling {1} ({1}, Discard this card: Search your library for a Forest card, reveal it, put it into your hand, then shuffle.)

Crypt Rats

{X}: Crypt Rats deals X damage to each creature and each player. Spend only black mana on X.

Swamp

Accursed Marauder

When Accursed Marauder enters, each player sacrifices a nontoken creature of their choice.

Battlefield Scrounger

Threshold — Put three cards from your graveyard on the bottom of your library: Battlefield Scrounger gets +3/+3 until end of turn. Activate only once each turn and only if seven or more cards are in your graveyard.

Fume Spitter

Sacrifice Fume Spitter: Put a -1/-1 counter on target creature.

Satyr Wayfinder

When Satyr Wayfinder enters, reveal the top four cards of your library. You may put a land card from among them into your hand. Put the rest into your graveyard.

Lotleth Giant

Undergrowth — When Lotleth Giant enters, it deals 1 damage to target opponent for each creature card in your graveyard.

Golgari Brownscale

When Golgari Brownscale is put into your hand from your graveyard, you gain 2 life.
Dredge 2 (If you would draw a card, you may mill two cards instead. If you do, return this card from your graveyard to your hand.)

Undertaker

{B}, {T}, Discard a card: Return target creature card from your graveyard to your hand.

Spore Frog

Sacrifice Spore Frog: Prevent all combat damage that would be dealt this turn.

Forest

Commune with the Gods

Reveal the top five cards of your library. You may put a creature or enchantment card from among them into your hand. Put the rest into your graveyard.

Faerie Macabre

Flying
Discard Faerie Macabre: Exile up to two target cards from graveyards.

Grave Scrabbler

Madness {1}{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.)
When Grave Scrabbler enters, if its madness cost was paid, you may return target creature card from a graveyard to its owner's hand.

Mournwhelk

When Mournwhelk enters, target player discards two cards.
Evoke {3}{B} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Stinkweed Imp

Flying
Whenever Stinkweed Imp deals combat damage to a creature, destroy that creature.
Dredge 5 (If you would draw a card, you may mill five cards instead. If you do, return this card from your graveyard to your hand.)

Tamiyo's Safekeeping

Target permanent you control gains hexproof and indestructible until end of turn. You gain 2 life. (A permanent with hexproof and indestructible can't be the target of spells or abilities your opponents control. Damage and effects that say "destroy" don't destroy it.)

Caustic Caterpillar

{1}{G}, Sacrifice Caustic Caterpillar: Destroy target artifact or enchantment.

Dread Return

Return target creature card from your graveyard to the battlefield.
Flashback—Sacrifice three creatures. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Gnaw to the Bone

You gain 2 life for each creature card in your graveyard.
Flashback {2}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Urborg Repossession

Kicker {1}{G} (You may pay an additional {1}{G} as you cast this spell.)
Return target creature card from your graveyard to your hand. You gain 2 life. If this spell was kicked, return another target permanent card from your graveyard to your hand.

Mesmeric Fiend

When Mesmeric Fiend enters, target opponent reveals their hand and you choose a nonland card from it. Exile that card.
When Mesmeric Fiend leaves the battlefield, return the exiled card to its owner's hand.

Vessel of Nascency

{1}{G}, Sacrifice Vessel of Nascency: Reveal the top four cards of your library. You may put an artifact, creature, enchantment, land, or planeswalker card from among them into your hand. Put the rest into your graveyard.

Sakura-Tribe Elder

Sacrifice Sakura-Tribe Elder: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Haunted Mire

({T}: Add {B} or {G}.)
Haunted Mire enters tapped.

Troll of Khazad-dûm

Troll of Khazad-dûm can't be blocked except by three or more creatures.
Swampcycling {1} ({1}, Discard this card: Search your library for a Swamp card, reveal it, put it into your hand, then shuffle.)

Tortured Existence

{B}, Discard a creature card: Return target creature card from your graveyard to your hand.