Spontaneous Mutation

Flash
Enchant creature
Enchanted creature gets -X/-0, where X is the number of cards in your graveyard.

King Narfi's Betrayal

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Each player mills four cards. Then you may exile a creature or planeswalker card from each graveyard.
II, III — Until end of turn, you may cast spells from among cards exiled with King Narfi's Betrayal, and you may spend mana as though it were mana of any color to cast those spells.

Thought Scour

Target player mills two cards.
Draw a card.

Logic Knot

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Counter target spell unless its controller pays {X}.

Skaab Ruinator

As an additional cost to cast this spell, exile three creature cards from your graveyard.
Flying
You may cast Skaab Ruinator from your graveyard.

Drowned Secrets

Whenever you cast a blue spell, target player mills two cards.

Tome Scour

Stitched Drake

As an additional cost to cast this spell, exile a creature card from your graveyard.
Flying

Frantic Inventory

Draw a card, then draw cards equal to the number of cards named Frantic Inventory in your graveyard.

Armored Skaab

When Armored Skaab enters, mill four cards.

Runechanter's Pike

Equipped creature has first strike and gets +X/+0, where X is the number of instant and sorcery cards in your graveyard.
Equip {2}

Corpse Churn

Mill three cards, then you may return a creature card from your graveyard to your hand. (To mill three cards, put the top three cards of your library into your graveyard.)

Headless Skaab

As an additional cost to cast this spell, exile a creature card from your graveyard.
Headless Skaab enters tapped.

Whispers of Emrakul

Target opponent discards a card at random.
Delirium — If there are four or more card types among cards in your graveyard, that player discards two cards at random instead.

Tymaret Calls the Dead

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Mill three cards. Then you may exile a creature or enchantment card from your graveyard. If you do, create a 2/2 black Zombie creature token.
III — You gain X life and scry X, where X is the number of Zombies you control.

Forever Young

Put any number of target creature cards from your graveyard on top of your library.
Draw a card.

Tasigur, the Golden Fang

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
{2}{G/U}{G/U}: Mill two cards, then return a nonland card of an opponent's choice from your graveyard to your hand.

Weigh Down

As an additional cost to cast this spell, exile a creature card from your graveyard.
Target creature gets -3/-3 until end of turn.

Dream Twist

Target player mills three cards.
Flashback {1}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Contingency Plan

Surveil 5. (Look at the top five cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

Treasure Cruise

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Draw three cards.

Chronic Flooding

Enchant land
Whenever enchanted land becomes tapped, its controller mills three cards.

Increasing Confusion

Target player mills X cards. If this spell was cast from a graveyard, that player mills twice that many cards instead.
Flashback {X}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Memory Sluice

Target player mills four cards.
Conspire (As you cast this spell, you may tap two untapped creatures you control that share a color with it. When you do, copy it and you may choose a new target for the copy.)

Shriekhorn

Shriekhorn enters with three charge counters on it.
{T}, Remove a charge counter from Shriekhorn: Target player mills two cards.