Snakeskin Veil

Put a +1/+1 counter on target creature you control. It gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Garruk, Unleashed

+1: Up to one target creature gets +3/+3 and gains trample until end of turn.
−2: Create a 3/3 green Beast creature token. Then if an opponent controls more creatures than you, put a loyalty counter on Garruk, Unleashed.
−7: You get an emblem with "At the beginning of your end step, you may search your library for a creature card, put it onto the battlefield, then shuffle."

Ajani's Comrade

Trample
At the beginning of combat on your turn, if you control an Ajani planeswalker, put a +1/+1 counter on Ajani's Comrade.

Awaken the Bear

Target creature gets +3/+3 and gains trample until end of turn.

Ram Through

Target creature you control deals damage equal to its power to target creature you don't control. If the creature you control has trample, excess damage is dealt to that creature's controller instead.

Managorger Hydra

Trample
Whenever a player casts a spell, put a +1/+1 counter on Managorger Hydra.

Run Afoul

Target opponent sacrifices a creature with flying.

Aspect of Hydra

Target creature gets +X/+X until end of turn, where X is your devotion to green. (Each {G} in the mana costs of permanents you control counts toward your devotion to green.)

Polukranos, Engine of Ruin

Reach, lifelink
Whenever Polukranos, Engine of Ruin or another nontoken Hydra you control dies, create a 3/3 green and white Phyrexian Hydra creature token with reach and a 3/3 green and white Phyrexian Hydra creature token with lifelink.

Polukranos Reborn

Reach
{6}{W/P}: Transform Polukranos Reborn. Activate only as a sorcery. ({W/P} can be paid with either {W} or 2 life.)