Esper Sentinel

Whenever an opponent casts their first noncreature spell each turn, draw a card unless that player pays {X}, where X is Esper Sentinel's power.

Krenko, Mob Boss

{T}: Create X 1/1 red Goblin creature tokens, where X is the number of Goblins you control.

Raid Bombardment

Whenever a creature you control with power 2 or less attacks, Raid Bombardment deals 1 damage to the player or planeswalker that creature is attacking.

Helm of the Host

At the beginning of combat on your turn, create a token that's a copy of equipped creature, except the token isn't legendary. That token gains haste.
Equip {5}

Soul's Attendant

Whenever another creature enters, you may gain 1 life.

Anger

Haste
As long as Anger is in your graveyard and you control a Mountain, creatures you control have haste.

Legion Loyalty

Creatures you control have myriad. (Whenever a creature with myriad attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)

Arabella, Abandoned Doll

Whenever Arabella, Abandoned Doll attacks, it deals X damage to each opponent and you gain X life, where X is the number of creatures you control with power 2 or less.

Goblin Bombardment

Sacrifice a creature: Goblin Bombardment deals 1 damage to any target.

Impact Tremors

Whenever a creature you control enters, Impact Tremors deals 1 damage to each opponent.

Selfless Spirit

Flying
Sacrifice Selfless Spirit: Creatures you control gain indestructible until end of turn.

The Jolly Balloon Man

Haste
{1}, {T}: Create a token that's a copy of another target creature you control, except it's a 1/1 red Balloon creature in addition to its other colors and types and it has flying and haste. Sacrifice it at the beginning of the next end step. Activate only as a sorcery.

Rhox Faithmender

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
If you would gain life, you gain twice that much life instead.

Soul Warden

Whenever another creature enters, you gain 1 life.

Mirror March

Whenever a nontoken creature you control enters, flip a coin until you lose a flip. For each flip you won, create a token that's a copy of that creature. Those tokens gain haste. Exile them at the beginning of the next end step.

Sol Ring

Krenko, Tin Street Kingpin

Whenever Krenko, Tin Street Kingpin attacks, put a +1/+1 counter on it, then create a number of 1/1 red Goblin creature tokens equal to Krenko's power.

Boromir, Warden of the Tower

Vigilance
Whenever an opponent casts a spell, if no mana was spent to cast it, counter that spell.
Sacrifice Boromir, Warden of the Tower: Creatures you control gain indestructible until end of turn. The Ring tempts you.

Marvin, Murderous Mimic

Marvin, Murderous Mimic has all activated abilities of creatures you control that don't have the same name as this creature.

Molten Echoes

As Molten Echoes enters, choose a creature type.
Whenever a nontoken creature you control of the chosen type enters, create a token that's a copy of that creature. That token gains haste. Exile it at the beginning of the next end step.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Mirror Box

The "legend rule" doesn't apply to permanents you control.
Each legendary creature you control gets +1/+1.
Each nontoken creature you control gets +1/+1 for each other creature you control with the same name as that creature.