Primal Cocoon

Enchant creature
At the beginning of your upkeep, put a +1/+1 counter on enchanted creature.
When enchanted creature attacks or blocks, sacrifice Primal Cocoon.

Barkhide Troll

Barkhide Troll enters with a +1/+1 counter on it.
{1}, Remove a +1/+1 counter from Barkhide Troll: Barkhide Troll gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Chlorophant

At the beginning of your upkeep, you may put a +1/+1 counter on Chlorophant.
Threshold — As long as seven or more cards are in your graveyard, Chlorophant has "At the beginning of your upkeep, you may put another +1/+1 counter on Chlorophant."

Fangren Firstborn

Whenever Fangren Firstborn attacks, put a +1/+1 counter on each attacking creature.

Cocoon

Enchant creature you control
When Cocoon enters, tap enchanted creature and put three pupa counters on Cocoon.
Enchanted creature doesn't untap during your untap step if Cocoon has a pupa counter on it.
At the beginning of your upkeep, remove a pupa counter from Cocoon. If you can't, sacrifice it, put a +1/+1 counter on enchanted creature, and that creature gains flying.

Forced Adaptation

Enchant creature
At the beginning of your upkeep, put a +1/+1 counter on enchanted creature.

Avatar of the Resolute

Reach, trample
Avatar of the Resolute enters with a +1/+1 counter on it for each other creature you control with a +1/+1 counter on it.

Baloth Pup

Baloth Pup has trample as long as it has a +1/+1 counter on it.

Bond Beetle

When Bond Beetle enters, put a +1/+1 counter on target creature.

Hardened Scales

If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on it instead.