Jelenn Sphinx

Flying, vigilance
Whenever Jelenn Sphinx attacks, other attacking creatures get +1/+1 until end of turn.

Aether Swooper

Flying
When Aether Swooper enters the battlefield, you get {E}{E} (two energy counters).
Whenever Aether Swooper attacks, you may pay {E}{E}. If you do, create a 1/1 colorless Servo artifact creature token.

Zealot il-Vec

Shadow (This creature can block or be blocked by only creatures with shadow.)
Whenever Zealot il-Vec attacks and isn't blocked, you may have it deal 1 damage to target creature. If you do, prevent all combat damage Zealot il-Vec would deal this turn.

Aven Courier

Flying
Whenever Aven Courier attacks, choose a counter on a permanent you control. Put a counter of that kind on target permanent you control if it doesn't have a counter of that kind on it.

Rigo, Streetwise Mentor

Rigo, Streetwise Mentor enters the battlefield with a shield counter on it. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)
Whenever you attack a player or planeswalker with one or more creatures with power 1 or less, draw a card.

Bess, Soul Nourisher

Whenever one or more other creatures with base power and toughness 1/1 enter the battlefield under your control, put a +1/+1 counter on Bess, Soul Nourisher.
Whenever Bess attacks, each other creature you control with base power and toughness 1/1 gets +X/+X until end of turn, where X is the number of +1/+1 counters on Bess.

Niblis of the Urn

Flying
Whenever Niblis of the Urn attacks, you may tap target creature.

Copperhorn Scout

Whenever Copperhorn Scout attacks, untap each other creature you control.

Hungry Spriggan

Trample
Whenever Hungry Spriggan attacks, it gets +3/+3 until end of turn.

Mirkwood Spider

Deathtouch
Whenever Mirkwood Spider attacks, target legendary creature you control gains deathtouch until end of turn.

Bishop of Binding

When Bishop of Binding enters the battlefield, 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.

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.)

Thalakos Deceiver

Shadow (This creature can block or be blocked by only creatures with shadow.)
Whenever Thalakos Deceiver attacks and isn't blocked, you may sacrifice it. If you do, gain control of target creature. (This effect lasts indefinitely.)

Soltari Trooper

Shadow (This creature can block or be blocked by only creatures with shadow.)
Whenever Soltari Trooper attacks, it gets +1/+1 until end of turn.