Arvinox, the Mind Flail

Arvinox, the Mind Flail isn't a creature unless you control three or more permanents you don't own.
At the beginning of your end step, exile the bottom card of each opponent's library face down. For as long as those cards remain exiled, you may look at them, you may cast permanent spells from among them, and you may spend mana as though it were mana of any color to cast those spells.

Desecration Demon

Flying
At the beginning of each combat, any opponent may sacrifice a creature. If a player does, tap Desecration Demon and put a +1/+1 counter on it.

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Blood Artist

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.

Vampire Scrivener

Flying
Whenever you gain life during your turn, put a +1/+1 counter on Vampire Scrivener.
Whenever you lose life during your turn, put a +1/+1 counter on Vampire Scrivener.

Worn Powerstone

Worn Powerstone enters tapped.
{T}: Add {C}{C}.

Graveyard Shift

This spell has flash as long as there are five or more mana values among cards in your graveyard.
Return target creature card from your graveyard to the battlefield.

Swamp

Kheru Mind-Eater

Menace
Whenever Kheru Mind-Eater deals combat damage to a player, that player exiles a card from their hand face down.
You may look at cards exiled with Kheru Mind-Eater, and you may play lands and cast spells from among those cards.

Dig Up the Body

Casualty 1 (As you cast this spell, you may sacrifice a creature with power 1 or greater. When you do, copy this spell.)
Mill two cards, then you may return a creature card from your graveyard to your hand. (To mill a card, put the top card of your library into your graveyard.)

Sol Ring

Grisly Sigil

Casualty 1 (As you cast this spell, you may sacrifice a creature with power 1 or greater. When you do, copy this spell and you may choose a new target for the copy.)
Choose target creature or planeswalker. If it was dealt noncombat damage this turn, Grisly Sigil deals 3 damage to it and you gain 3 life. Otherwise, Grisly Sigil deals 1 damage to it and you gain 1 life.