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.

Nyx-Fleece Ram

At the beginning of your upkeep, you gain 1 life.

Keleth, Sunmane Familiar

Whenever a commander you control attacks, put a +1/+1 counter on it.
Partner (You can have two commanders if both have partner.)

Academy Manufactor

If you would create a Clue, Food, or Treasure token, instead create one of each.

Mangara, the Diplomat

Lifelink
Whenever an opponent attacks with creatures, if two or more of those creatures are attacking you and/or planeswalkers you control, draw a card.
Whenever an opponent casts their second spell each turn, draw a card.

Whitemane Lion

Flash
When Whitemane Lion enters, return a creature you control to its owner's hand.

Bishop of Binding

When Bishop of Binding enters, exile target creature an opponent controls until Bishop of Binding leaves the battlefield.
Whenever Bishop of Binding attacks, target Vampire gets +X/+X until end of turn, where X is the power of the exiled card.

Wyrm's Crossing Patrol

Myriad (Whenever this creature 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.)

Arashin Foremost

Double strike
Whenever Arashin Foremost enters or attacks, another target Warrior creature you control gains double strike until end of turn.

Delney, Streetwise Lookout

Creatures you control with power 2 or less can't be blocked by creatures with power 3 or greater.
If an ability of a creature you control with power 2 or less triggers, that ability triggers an additional time.

Tegan Jovanka

Brave Heart — Whenever you attack, target attacking historic creature gets +1/+1 and gains indestructible until end of turn. (Artifacts, legendaries, and Sagas are historic.)
Doctor's companion (You can have two commanders if the other is the Doctor.)

Dauntless Aven

Flying
Whenever Dauntless Aven attacks, untap target creature you control.

Linden, the Steadfast Queen

Vigilance (Attacking doesn't cause this creature to tap.)
Whenever a white creature you control attacks, you gain 1 life.

Anafenza, Kin-Tree Spirit

Whenever another nontoken creature you control enters, bolster 1. (Choose a creature with the least toughness among creatures you control and put a +1/+1 counter on it.)

Spirited Companion

When Spirited Companion enters, draw a card.

Skrelv, Defector Mite

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
Skrelv, Defector Mite can't block.
{W/P}, {T}: Choose a color. Another target creature you control gains toxic 1 and hexproof from that color until end of turn. It can't be blocked by creatures of that color this turn. ({W/P} can be paid with either {W} or 2 life.)

Tyr's Blessing

Target creature gains indestructible until end of turn. (Then exile this card. You may cast the creature later from exile.)

Blessed Hippogriff

Flying
Whenever Blessed Hippogriff attacks, target attacking creature without flying gains flying until end of turn.

Blessed Hippogriff // Tyr's Blessing

Baldin, Century Herdmaster

As long as it's your turn, each creature assigns combat damage equal to its toughness rather than its power.
Whenever Baldin, Century Herdmaster attacks, up to one hundred target creatures each get +0/+X until end of turn, where X is the number of cards in your hand.

Bola Slinger

Backup 1 (When this creature enters, put a +1/+1 counter on target creature. If that's another creature, it gains the following ability until end of turn.)
Whenever this creature attacks, tap target artifact or creature an opponent controls.

Adaptive Shimmerer

Flash
Adaptive Shimmerer enters with three +1/+1 counters on it.

Brigid, Hero of Kinsbaile

First strike
{T}: Brigid, Hero of Kinsbaile deals 2 damage to each attacking or blocking creature target player controls.

Eight-and-a-Half-Tails

{1}{W}: Target permanent you control gains protection from white until end of turn.
{1}: Target spell or permanent becomes white until end of turn.

Alaborn Cavalier

Whenever Alaborn Cavalier attacks, you may tap target creature.

Siege Striker

Double strike (This creature deals both first-strike and regular combat damage.)
Whenever Siege Striker attacks, you may tap any number of untapped creatures you control. Siege Striker gets +1/+1 until end of turn for each creature tapped this way.