Seed the Land

Whenever a land enters, its controller creates a 1/1 green Snake creature token.

Shizuko, Caller of Autumn

At the beginning of each player's upkeep, that player adds {G}{G}{G}. Until end of turn, they don't lose this mana as steps and phases end.

Shisato, Whispering Hunter

At the beginning of your upkeep, sacrifice a Snake.
Whenever Shisato, Whispering Hunter deals combat damage to a player, that player skips their next untap step.

Lure

Enchant creature
All creatures able to block enchanted creature do so.

Sachi, Daughter of Seshiro

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

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 Orochi Eggwatcher.

Orochi Eggwatcher // Shidako, Broodmistress

Sasaya's Essence

Whenever a land you control is tapped for mana, add an additional one mana of any type that land produced for each other land you control with the same name as it.

Sasaya, Orochi Ascendant

Reveal your hand: If you have seven or more land cards in your hand, flip Sasaya, Orochi Ascendant.

Sasaya, Orochi Ascendant // Sasaya's Essence

Kashi-Tribe Reaver

Whenever Kashi-Tribe Reaver deals combat damage to a creature, tap that creature and it doesn't untap during its controller's next untap step.
{1}{G}: Regenerate Kashi-Tribe Reaver.

Rending Vines

Destroy target artifact or enchantment if its mana value is less than or equal to the number of cards in your hand.
Draw a card.

Endless Swarm

Create a 1/1 green Snake creature token for each card in your hand.
Epic (For the rest of the game, you can't cast spells. At the beginning of each of your upkeeps, copy this spell except for its epic ability.)

Sakura-Tribe Elder

Sacrifice Sakura-Tribe Elder: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Sakura-Tribe Scout

{T}: You may put a land card from your hand onto the battlefield.

Molting Skin

Return Molting Skin to its owner's hand: Regenerate target creature.

Forest

Sakiko, Mother of Summer

Whenever a creature you control deals combat damage to a player, add that much {G}. Until end of turn, you don't lose this mana as steps and phases end.

Sakura-Tribe Springcaller

At the beginning of your upkeep, add {G}. Until end of turn, you don't lose this mana as steps and phases end.

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.

Sosuke's Summons

Create two 1/1 green Snake creature tokens.
Whenever a nontoken Snake you control enters, you may return Sosuke's Summons from your graveyard to your hand.

Time of Need

Search your library for a legendary creature card, reveal it, put it into your hand, then shuffle.

Kashi-Tribe Elite

Legendary Snakes you control have shroud. (They can't be the targets of spells or abilities.)
Whenever Kashi-Tribe Elite deals combat damage to a creature, tap that creature and it doesn't untap during its controller's next untap step.

Orochi Hatchery

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

Enshrined Memories

Reveal the top X cards of your library. Put all creature cards revealed this way into your hand and the rest on the bottom of your library in any order.

Commune with Nature

Look at the top five cards of your library. You may reveal a creature card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

Matsu-Tribe Decoy

{2}{G}: Target creature blocks Matsu-Tribe Decoy this turn if able.
Whenever Matsu-Tribe Decoy deals combat damage to a creature, tap that creature and it doesn't untap during its controller's next untap step.

Patron of the Orochi

Snake offering (You may cast this spell any time you could cast an instant by sacrificing a Snake and paying the difference in mana costs between this and the sacrificed Snake. Mana cost includes color.)
{T}: Untap all Forests and all green creatures. Activate only once each turn.

Serpent Skin

Flash
Enchant creature
Enchanted creature gets +1/+1.
{G}: Regenerate enchanted creature.

Orochi Sustainer

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.

Nature's Will

Whenever one or more creatures you control deal combat damage to a player, tap all lands that player controls and untap all lands you control.

Matsu-Tribe Sniper

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