Withengar Unbound

Flying, intimidate, trample (A creature with intimidate can't be blocked except by artifact creatures and/or creatures that share a color with it.)
Whenever a player loses the game, put thirteen +1/+1 counters on Withengar Unbound.

Elbrus, the Binding Blade

Equipped creature gets +1/+0.
When equipped creature deals combat damage to a player, unattach Elbrus, then transform it.
Equip {1}

Elbrus, the Binding Blade // Withengar Unbound

Lazav, Dimir Mastermind

Hexproof
Whenever a creature card is put into an opponent's graveyard from anywhere, you may have Lazav become a copy of that card, except its name is Lazav, Dimir Mastermind, it's legendary in addition to its other types, and it has hexproof and this ability.

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.)

Filigree Familiar

When this creature enters, you gain 2 life.
When this creature dies, draw a card.

Mirari

Whenever you cast an instant or sorcery spell, you may pay {3}. If you do, copy that spell. You may choose new targets for the copy.

Dimir Aqueduct

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {U}{B}.

Curse of the Bloody Tome

Enchant player
At the beginning of enchanted player's upkeep, that player mills two cards.

Tome Scour

Psychic Strike

Counter target spell. Its controller mills two cards.

Swamp

Fog Bank

Defender (This creature can't attack.)
Flying
Prevent all combat damage that would be dealt to and dealt by this creature.

Memory Erosion

Whenever an opponent casts a spell, that player mills two cards.

Dismal Backwater

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {U} or {B}.

Hedron Crab

Landfall — Whenever a land you control enters, target player mills three cards. (They put the top three cards of their library into their graveyard.)

Paranoid Delusions

Target player mills three cards.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)

Jace's Phantasm

Flying
This creature gets +4/+4 as long as an opponent has ten or more cards in their graveyard.

Sands of Delirium

Consuming Aberration

Consuming Aberration's power and toughness are each equal to the number of cards in your opponents' graveyards.
Whenever you cast a spell, each opponent reveals cards from the top of their library until they reveal a land card, then puts those cards into their graveyard.

Island

Trepanation Blade

Whenever equipped creature attacks, defending player reveals cards from the top of their library until they reveal a land card. The creature gets +1/+0 until end of turn for each card revealed this way. That player puts the revealed cards into their graveyard.
Equip {2}

Drowned Catacomb

This land enters tapped unless you control an Island or a Swamp.
{T}: Add {U} or {B}.

Invisibility

Enchant creature
Enchanted creature can't be blocked except by Walls.

Keening Stone

{5}, {T}: Target player mills X cards, where X is the number of cards in that player's graveyard.

Traumatize

Target player mills half their library, rounded down.

Visions of Beyond

Draw a card. If a graveyard has twenty or more cards in it, draw three cards instead.

Psychic Drain

Target player mills X cards and you gain X life.

Mind Grind

Each opponent reveals cards from the top of their library until they reveal X land cards, then puts all cards revealed this way into their graveyard. X can't be 0.

Perplex

Counter target spell unless its controller discards their hand.
Transmute {1}{U}{B} ({1}{U}{B}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Counterspell

Triton Shorestalker

Wight of Precinct Six

This creature gets +1/+1 for each creature card in your opponents' graveyards.

Mind Funeral

Target opponent reveals cards from the top of their library until four land cards are revealed. That player puts all cards revealed this way into their graveyard.

Evil Twin

You may have this creature enter as a copy of any creature on the battlefield, except it has "{U}{B}, {T}: Destroy target creature with the same name as this creature."

Trespassing Souleater

{U/P}: This creature can't be blocked this turn. ({U/P} can be paid with either {U} or 2 life.)