Careful Study

Narcomoeba

Flying
When Narcomoeba is put into your graveyard from your library, you may put it onto the battlefield.

Poxwalkers

Deathtouch
Curse of the Walking Pox — Whenever you cast a spell from anywhere other than your hand, return Poxwalkers from your graveyard to the battlefield tapped.

Bridge from Below

Whenever a nontoken creature is put into your graveyard from the battlefield, if Bridge from Below is in your graveyard, create a 2/2 black Zombie creature token.
When a creature is put into an opponent's graveyard from the battlefield, if Bridge from Below is in your graveyard, exile Bridge from Below.

Hogaak, Arisen Necropolis

You can't spend mana to cast this spell.
Convoke, delve (Each creature you tap while casting this spell pays for {1} or one mana of that creature's color. Each card you exile from your graveyard pays for {1}.)
You may cast Hogaak, Arisen Necropolis from your graveyard.
Trample

Golgari Grave-Troll

Golgari Grave-Troll enters with a +1/+1 counter on it for each creature card in your graveyard.
{1}, Remove a +1/+1 counter from Golgari Grave-Troll: Regenerate Golgari Grave-Troll.
Dredge 6 (If you would draw a card, you may mill six cards instead. If you do, return this card from your graveyard to your hand.)

Swamp

Flame-Kin Zealot

When Flame-Kin Zealot enters, creatures you control get +1/+1 and gain haste until end of turn.

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.)

Island

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.)

Tolarian Winds

Discard all the cards in your hand, then draw that many cards.

Breakthrough

Draw four cards, then choose X cards in your hand and discard the rest.

Prized Amalgam

Whenever a creature enters, if it entered from your graveyard or you cast it from your graveyard, return Prized Amalgam from your graveyard to the battlefield tapped at the beginning of the next end step.

Cabal Therapy

Choose a nonland card name. Target player reveals their hand and discards all cards with that name.
Flashback—Sacrifice a creature. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Golgari Thug

When Golgari Thug dies, put target creature card from your graveyard on top of your library.
Dredge 4 (If you would draw a card, you may mill four cards instead. If you do, return this card from your graveyard to your hand.)

Otherworldly Gaze

Surveil 3. (Look at the top three cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)
Flashback {1}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)