Boros Mastiff

Battalion — Whenever this creature and at least two other creatures attack, this creature gains lifelink until end of turn. (Damage dealt by a creature with lifelink also causes its controller to gain that much life.)

Wake the Reflections

Populate. (Create a token that's a copy of a creature token you control.)

Savageborn Hydra

Double strike
This creature enters with X +1/+1 counters on it.
{1}{R/G}: Put a +1/+1 counter on this creature. Activate only as a sorcery.

Scab-Clan Giant

When this creature enters, it fights target creature an opponent controls chosen at random.

Showstopper

Until end of turn, creatures you control gain "When this creature dies, it deals 2 damage to target creature an opponent controls."

Sin Collector

When this creature enters, target opponent reveals their hand. You choose an instant or sorcery card from it and exile that card.

Sire of Insanity

At the beginning of each end step, each player discards their hand.

Species Gorger

At the beginning of your upkeep, return a creature you control to its owner's hand.

Spike Jester

Tajic, Blade of the Legion

Indestructible
Battalion — Whenever Tajic and at least two other creatures attack, Tajic gets +5/+5 until end of turn.

Spirit

Teysa, Envoy of Ghosts

Vigilance, protection from creatures
Whenever a creature deals combat damage to you, destroy that creature. Create a 1/1 white and black Spirit creature token with flying.

Tithe Drinker

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)

Aetherling

{U}: Exile this creature. Return it to the battlefield under its owner's control at the beginning of the next end step.
{U}: This creature can't be blocked this turn.
{1}: This creature gets +1/-1 until end of turn.
{1}: This creature gets -1/+1 until end of turn.

Knight

Trostani's Summoner

Rhino

Centaur

When this creature enters, create a 2/2 white Knight creature token with vigilance, a 3/3 green Centaur creature token, and a 4/4 green Rhino creature token with trample.

Unflinching Courage

Enchant creature
Enchanted creature gets +2/+2 and has trample and lifelink. (Damage dealt by the creature also causes its controller to gain that much life.)

Varolz, the Scar-Striped

Each creature card in your graveyard has scavenge. The scavenge cost is equal to its mana cost. (Exile a creature card from your graveyard and pay its mana cost: Put a number of +1/+1 counters equal to that card's power on target creature. Scavenge only as a sorcery.)
Sacrifice another creature: Regenerate Varolz.

Dragon's Maze