Star Pupil

Star Pupil enters with a +1/+1 counter on it.
When Star Pupil dies, put its counters on target creature you control.

Angelic Cub

Whenever Angelic Cub becomes the target of a spell or ability for the first time each turn, put a +1/+1 counter on it.
As long as Angelic Cub has three or more +1/+1 counters on it, it has flying.

Swift Response

Patron of the Valiant

Flying
When Patron of the Valiant enters, put a +1/+1 counter on each creature you control with a +1/+1 counter on it.

Generous Pup

Vigilance
Whenever one or more +1/+1 counters are put on Generous Pup, put a +1/+1 counter on each other creature you control. This ability triggers only once each turn.

Have

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.

Battlefield Promotion

Put a +1/+1 counter on target creature. That creature gains first strike until end of turn. You gain 2 life. (A creature with first strike deals combat damage before creatures without first strike.)

Stalwart

Take Up the Shield

Put a +1/+1 counter on target creature. It gains lifelink and indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Plains

Cave of Temptation

{T}: Add {C}.
{1}, {T}: Add one mana of any color.
{4}, {T}, Sacrifice Cave of Temptation: Put two +1/+1 counters on target creature. Activate only as a sorcery.

Basri's Lieutenant

Vigilance, protection from multicolored
When Basri's Lieutenant enters, put a +1/+1 counter on target creature you control.
Whenever Basri's Lieutenant or another creature you control dies, if it had a +1/+1 counter on it, create a 2/2 white Knight creature token with vigilance.

Mikaeus, the Lunarch

Mikaeus, the Lunarch enters with X +1/+1 counters on it.
{T}: Put a +1/+1 counter on Mikaeus.
{T}, Remove a +1/+1 counter from Mikaeus: Put a +1/+1 counter on each other creature you control.

Urdnan, Dromoka Warrior

When Urdnan, Dromoka Warrior enters, put a +1/+1 counter on target creature.
Whenever you attack, target attacking creature with a +1/+1 counter on it gains first strike until end of turn. If that creature has two or more +1/+1 counters on it, it gains double strike until end of turn instead.

Jubilant Mascot

At the beginning of combat on your turn, you may pay {3}{W}. If you do, support 2. (Put a +1/+1 counter on each of up to two other target creatures.)

Basri's Solidarity

Put a +1/+1 counter on each creature you control.