Luxior, Giada's Gift

Equipped creature gets +1/+1 for each counter on it.
Equipped permanent isn't a planeswalker and is a creature in addition to its other types. (Loyalty abilities can still be activated.)
Equip planeswalker {1}
Equip {3}

The Scorpion God

Whenever a creature with a -1/-1 counter on it dies, draw a card.
{1}{B}{R}: Put a -1/-1 counter on another target creature.
When The Scorpion God dies, return it to its owner's hand at the beginning of the next end step.

Everlasting Torment

Players can't gain life.
Damage can't be prevented.
All damage is dealt as though its source had wither. (A source with wither deals damage to creatures in the form of -1/-1 counters.)

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Vicious Shadows

Whenever a creature dies, you may have this enchantment deal damage to target player equal to the number of cards in that player's hand.

Crumbling Ashes

At the beginning of your upkeep, destroy target creature with a -1/-1 counter on it.

Puppeteer Clique

Flying
When this creature enters, put target creature card from an opponent's graveyard onto the battlefield under your control. It gains haste. At the beginning of your next end step, exile it.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Rise of the Dark Realms

Put all creature cards from all graveyards onto the battlefield under your control.

Harbinger of Night

At the beginning of your upkeep, put a -1/-1 counter on each creature.

Blowfly Infestation

Whenever a creature dies, if it had a -1/-1 counter on it, put a -1/-1 counter on target creature.

Mikaeus, the Unhallowed

Intimidate (This creature can't be blocked except by artifact creatures and/or creatures that share a color with it.)
Whenever a Human deals damage to you, destroy it.
Other non-Human creatures you control get +1/+1 and have undying. (When a creature with undying dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Phyrexian Crusader

First strike, protection from red and from white
Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

Tempt with Vengeance

Tempting offer — Create X 1/1 red Elemental creature tokens with haste. Each opponent may create X 1/1 red Elemental creature tokens with haste. For each opponent who does, create X 1/1 red Elemental creature tokens with haste.