Have

Sosuke, Son of Seshiro

Other Snake creatures you control get +1/+0.
Whenever a Warrior you control deals combat damage to a creature, destroy that creature at end of combat.

Snake Umbra

Enchant creature
Enchanted creature gets +1/+1 and has "Whenever this creature deals damage to an opponent, you may draw a card."
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Death-Hood Cobra

{1}{G}: This creature gains reach until end of turn.
{1}{G}: This creature gains deathtouch until end of turn.

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.)

Sachi, Daughter of Seshiro

Other Snake creatures you control get +0/+1.
Shamans you control have "{T}: Add {G}{G}."

Harmonize

Desert

{T}: Add {C}.
{T}: This land deals 1 damage to target attacking creature. Activate only during the end of combat step.

Snakeform

Until end of turn, target creature loses all abilities and becomes a green Snake with base power and toughness 1/1.
Draw a card.

Seshiro the Anointed

Other Snake creatures you control get +2/+2.
Whenever a Snake you control deals combat damage to a player, you may draw a card.

Animal Sanctuary

{T}: Add {C}.
{2}, {T}: Put a +1/+1 counter on target Bird, Cat, Dog, Goat, Ox, or Snake.

Hashep Oasis

{T}: Add {C}.
{T}, Pay 1 life: Add {G}.
{1}{G}{G}, {T}, Sacrifice a Desert: Target creature gets +3/+3 until end of turn. Activate only as a sorcery.

Forest

Ramunap Hydra

Vigilance, reach, trample
This creature gets +1/+1 as long as you control a Desert.
This creature gets +1/+1 as long as there is a Desert card in your graveyard.

Ohran Viper

Whenever this creature deals combat damage to a creature, destroy that creature at end of combat.
Whenever this creature deals combat damage to a player, you may draw a card.

Prey Upon

Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.)

Sakura-Tribe Elder

Sacrifice this creature: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Abundant Harvest

Choose land or nonland. Reveal cards from the top of your library until you reveal a card of the chosen kind. Put that card into your hand and the rest on the bottom of your library in a random order.

Masked Vandal

Changeling (This card is every creature type.)
When this creature enters, you may exile a creature card from your graveyard. If you do, exile target artifact or enchantment an opponent controls.

Orochi Sustainer

Desert of the Indomitable

This land enters tapped.
{T}: Add {G}.
Cycling {1}{G} ({1}{G}, Discard this card: Draw a card.)