Ob Nixilis, Unshackled

Flying, trample
Whenever an opponent searches their library, that player sacrifices a creature of their choice and loses 10 life.
Whenever another creature dies, put a +1/+1 counter on Ob Nixilis.

The Red Terror

Advanced Species — Whenever a red source you control deals damage to one or more permanents and/or players, put a +1/+1 counter on The Red Terror.

Dragon Throne of Tarkir

Equipped creature has defender and "{2}, {T}: Other creatures you control gain trample and get +X/+X until end of turn, where X is this creature's power."
Equip {3}

Sulfuric Vortex

At the beginning of each player's upkeep, this enchantment deals 2 damage to that player.
If a player would gain life, that player gains no life instead.

Razorkin Needlehead

This creature has first strike during your turn.
Whenever an opponent draws a card, this creature deals 1 damage to them.

Auntie Blyte, Bad Influence

Flying
Whenever a source you control deals damage to you, put that many +1/+1 counters on Auntie Blyte.
{1}{R}, {T}, Remove X +1/+1 counters from Auntie Blyte: It deals X damage to any target.

Zo-Zu the Punisher

Whenever a land enters, Zo-Zu deals 2 damage to that land's controller.

War Elemental

When this creature enters, sacrifice it unless an opponent was dealt damage this turn.
Whenever an opponent is dealt damage, put that many +1/+1 counters on this creature.

Underworld Dreams

Whenever an opponent draws a card, this enchantment deals 1 damage to that player.

Shadowspear

Equipped creature gets +1/+1 and has trample and lifelink.
{1}: Permanents your opponents control lose hexproof and indestructible until end of turn.
Equip {2}

Painful Quandary

Whenever an opponent casts a spell, that player loses 5 life unless they discard a card.

Psychosis Crawler

Psychosis Crawler's power and toughness are each equal to the number of cards in your hand.
Whenever you draw a card, each opponent loses 1 life.