Riot Ringleader

Whenever Riot Ringleader attacks, Human creatures you control get +1/+0 until end of turn.

Banners Raised

Creatures you control get +1/+0 until end of turn.

Commander's Authority

Enchant creature
Enchanted creature has "At the beginning of your upkeep, create a 1/1 white Human creature token."

Goldnight Commander

Whenever another creature you control enters, creatures you control get +1/+1 until end of turn.

Thatcher Revolt

Create three 1/1 red Human creature tokens with haste. Sacrifice those tokens at the beginning of the next end step.

Somberwald Vigilante

Whenever Somberwald Vigilante becomes blocked by a creature, Somberwald Vigilante deals 1 damage to that creature.

Mountain

Midnight Duelist

Kruin Striker

Whenever another creature you control enters, Kruin Striker gets +1/+0 and gains trample until end of turn. (It can deal excess combat damage to the player or planeswalker it's attacking.)

Kessig Malcontents

When Kessig Malcontents enters, it deals damage to target player or planeswalker equal to the number of Humans you control.

Plains

Nearheath Pilgrim

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as Nearheath Pilgrim is paired with another creature, both creatures have lifelink.

Vigilante Justice

Whenever a Human you control enters, Vigilante Justice deals 1 damage to any target.