Dread Return

Return target creature card from your graveyard to the battlefield.
Flashback—Sacrifice three creatures. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Lotleth Giant

Undergrowth — When Lotleth Giant enters the battlefield, it deals 1 damage to target opponent for each creature card in your graveyard.

Dark Ritual

Swamp

Ulamog's Crusher

Annihilator 2 (Whenever this creature attacks, defending player sacrifices two permanents.)
Ulamog's Crusher attacks each combat if able.

Mountain

Exhume

Each player puts a creature card from their graveyard onto the battlefield.

Eldrazi Devastator

Stinkweed Imp

Flying
Whenever Stinkweed Imp deals combat damage to a creature, destroy that creature.
Dredge 5 (If you would draw a card, you may mill five cards instead. If you do, return this card from your graveyard to your hand.)

Faithless Looting

Draw two cards, then discard two cards.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Insolent Neonate

Menace (This creature can't be blocked except by two or more creatures.)
Discard a card, Sacrifice Insolent Neonate: Draw a card.

Tormenting Voice

As an additional cost to cast this spell, discard a card.
Draw two cards.

Dragon Breath

Enchant creature
Enchanted creature has haste.
{R}: Enchanted creature gets +1/+0 until end of turn.
When a creature with mana value 6 or greater enters the battlefield, you may return Dragon Breath from your graveyard to the battlefield attached to that creature.