Have

Molting Snakeskin

Enchant creature
Enchanted creature gets +2/+0 and has "{2}{B}: Regenerate this creature."

Orochi Sustainer

Sachi, Daughter of Seshiro

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

Wild Hunger

Target creature gets +3/+1 and gains trample until end of turn.
Flashback {3}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Python

Turntimber Basilisk

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
Landfall — Whenever a land you control enters, you may have target creature block this creature this turn if able.

Vizier of the Menagerie

You may look at the top card of your library any time.
You may cast creature spells from the top of your library.
You can spend mana of any type to cast creature spells.

Snake Basket

{X}, Sacrifice this artifact: Create X 1/1 green Snake creature tokens. Activate only as a sorcery.

Mystic Snake

Flash
When this creature enters, counter target spell.

Sosuke's Summons

Create two 1/1 green Snake creature tokens.
Whenever a nontoken Snake you control enters, you may return this card from your graveyard to your hand.

Lorescale Coatl

Whenever you draw a card, put a +1/+1 counter on this creature.

Ambush Viper

Stonecoil Serpent

Reach, trample, protection from multicolored
This creature enters with X +1/+1 counters on it.

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.

Lotus Cobra

Landfall — Whenever a land you control enters, add one mana of any color.

Patagia Viper

Flying
When this creature enters, create two 1/1 green and blue Snake creature tokens.
When this creature enters, sacrifice it unless {U} was spent to cast it.

River Boa

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
{G}: Regenerate this creature.

Coiling Oracle

When this creature enters, reveal the top card of your library. If it's a land card, put it onto the battlefield. Otherwise, put that card into your hand.

Saryth, the Viper's Fang

Other tapped creatures you control have deathtouch.
Other untapped creatures you control have hexproof.
{1}, {T}: Untap another target creature or land you control.

Blight Mamba

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
{1}{G}: Regenerate this creature.

Noose Constrictor

Reach
Discard a card: This creature gets +1/+1 until end of turn.

Ramunap Excavator

Orochi Hatchery

This artifact enters with X charge counters on it.
{5}, {T}: Create a 1/1 green Snake creature token for each charge counter on this artifact.

Marsh Boa

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)

Cobra Trap

If a noncreature permanent under your control was destroyed this turn by a spell or ability an opponent controlled, you may pay {G} rather than pay this spell's mana cost.
Create four 1/1 green Snake creature tokens.

Matsu-Tribe Sniper

{T}: This creature deals 1 damage to target creature with flying.
Whenever this creature deals damage to a creature, tap that creature and it doesn't untap during its controller's next untap step.

Shidako, Broodmistress

{G}, Sacrifice a creature: Target creature gets +3/+3 until end of turn.

Orochi Eggwatcher

{2}{G}, {T}: Create a 1/1 green Snake creature token. If you control ten or more creatures, flip this creature.

Orochi Eggwatcher // Shidako, Broodmistress

Broodbirth Viper

Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
Whenever this creature deals combat damage to a player, you may draw a card.

Sultai Flayer

Whenever a creature you control with toughness 4 or greater dies, you gain 4 life.

Honored Hydra

Trample
Embalm {3}{G} ({3}{G}, Exile this card from your graveyard: Create a token that's a copy of it, except it's a white Zombie Snake Hydra with no mana cost. Embalm only as a sorcery.)