Lightwalker

Lightwalker has flying as long as it has a +1/+1 counter on it.

High Sentinels of Arashin

Flying
High Sentinels of Arashin gets +1/+1 for each other creature you control with a +1/+1 counter on it.
{3}{W}: Put a +1/+1 counter on target creature.

Long Road Home

Exile target creature. At the beginning of the next end step, return that card to the battlefield under its owner's control with a +1/+1 counter on it.

Trusty Retriever

When Trusty Retriever enters, choose one —
• Put a +1/+1 counter on Trusty Retriever.
• Return target artifact or enchantment card from your graveyard to your hand.

Tempered Veteran

{W}, {T}: Put a +1/+1 counter on target creature with a +1/+1 counter on it.
{4}{W}{W}, {T}: Put a +1/+1 counter on target creature.

Swift Response

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.

Basri's Acolyte

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
When Basri's Acolyte enters, put a +1/+1 counter on each of up to two other target creatures you control.

Plains

Bulwark Giant

When Bulwark Giant enters, you gain 5 life.

Duelist's Heritage

Whenever one or more creatures attack, you may have target attacking creature gain double strike until end of turn.

Makeshift Battalion

Battalion — Whenever Makeshift Battalion and at least two other creatures attack, put a +1/+1 counter on Makeshift Battalion.

Thriving Heath

Thriving Heath enters tapped. As it enters, choose a color other than white.
{T}: Add {W} or one mana of the chosen color.

Supply Runners

When Supply Runners enters, put a +1/+1 counter on each other creature you control.