Avatar of Woe

If there are ten or more creature cards total in all graveyards, this spell costs {6} less to cast.
Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
{T}: Destroy target creature. It can't be regenerated.

Perpetual Timepiece

{T}: Mill two cards.
{2}, Exile Perpetual Timepiece: Shuffle any number of target cards from your graveyard into your library.

Bonehoard

Living weapon (When this Equipment enters, create a 0/0 black Phyrexian Germ creature token, then attach this to it.)
Equipped creature gets +X/+X, where X is the number of creature cards in all graveyards.
Equip {2}

Meren of Clan Nel Toth

Whenever another creature you control dies, you get an experience counter.
At the beginning of your end step, choose target creature card in your graveyard. If that card's mana value is less than or equal to the number of experience counters you have, return it to the battlefield. Otherwise, put it into your hand.

Lord of Extinction

Lord of Extinction's power and toughness are each equal to the number of cards in all graveyards.

Kessig Cagebreakers

Whenever Kessig Cagebreakers attacks, create a 2/2 green Wolf creature token that's tapped and attacking for each creature card in your graveyard.

Ghoultree

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

Daemogoth Titan

Whenever Daemogoth Titan attacks or blocks, sacrifice a creature.

Deathbloom Ritualist

{T}: Add X mana of any one color, where X is the number of creature cards in your graveyard.