Llanowar Elves

Hydra's Growth

Enchant creature
When Hydra's Growth enters, put a +1/+1 counter on enchanted creature.
At the beginning of your upkeep, double the number of +1/+1 counters on enchanted creature.

Fyndhorn Elves

Fractal Harness

When Fractal Harness enters, create a 0/0 green and blue Fractal creature token. Put X +1/+1 counters on it and attach Fractal Harness to it.
Whenever equipped creature attacks, double the number of +1/+1 counters on it.
Equip {2}

Mage Slayer

Whenever equipped creature attacks, it deals damage equal to its power to the player or planeswalker it's attacking.
Equip {3}

Krenko, Tin Street Kingpin

Whenever Krenko, Tin Street Kingpin attacks, put a +1/+1 counter on it, then create a number of 1/1 red Goblin creature tokens equal to Krenko's power.

Elvish Mystic

Highland Forest

({T}: Add {R} or {G}.)
Highland Forest enters tapped.

Sol Ring

Gruul Guildgate

This land enters tapped.
{T}: Add {R} or {G}.

Forest

Shock

Thorn Elemental

You may have Thorn Elemental assign its combat damage as though it weren't blocked.