Marsh Viper

Whenever Marsh Viper deals damage to a player, that player gets two poison counters. (A player with ten or more poison counters loses the game.)

Ohran Viper

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

Ohran Frostfang

Attacking creatures you control have deathtouch.
Whenever a creature you control deals combat damage to a player, draw a card.

Pharika's Chosen

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Anaconda

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

Krosan Constrictor

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
{T}: Target black creature gets -2/-0 until end of turn.

Lonis, Cryptozoologist

Whenever another nontoken creature you control enters, investigate.
{T}, Sacrifice X Clues: Target opponent reveals the top X cards of their library. You may put a nonland permanent card with mana value X or less from among them onto the battlefield under your control. That player puts the rest on the bottom of their library in a random order.

Coiling Oracle

When Coiling Oracle 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.

Nessian Asp

Reach
{6}{G}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.)

Mystic Snake

Flash
When Mystic Snake enters, counter target spell.

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 Blight Mamba.

Ophidian

Whenever Ophidian attacks and isn't blocked, you may draw a card. If you do, Ophidian assigns no combat damage this turn.

Moss Viper

Nemesis of Mortals

This spell costs {1} less to cast for each creature card in your graveyard.
{7}{G}{G}: Monstrosity 5. This ability costs {1} less to activate for each creature card in your graveyard. (If this creature isn't monstrous, put five +1/+1 counters on it and it becomes monstrous.)

Rotting Fensnake

Winding Constrictor

If one or more counters would be put on an artifact or creature you control, that many plus one of each of those kinds of counters are put on that permanent instead.
If you would get one or more counters, you get that many plus one of each of those kinds of counters instead.

Hexdrinker

Level up {1} ({1}: Put a level counter on this. Level up only as a sorcery.)
LEVEL 3-7
4/4
Protection from instants
LEVEL 8+
6/6
Protection from everything

Lorescale Coatl

Whenever you draw a card, put a +1/+1 counter on Lorescale Coatl.

Crypt Cobra

Whenever Crypt Cobra attacks and isn't blocked, defending player gets a poison counter. (A player with ten or more poison counters loses the game.)

Fire Snake

When Fire Snake dies, destroy target land.

Wasteland Viper

Deathtouch
Bloodrush — {G}, Discard Wasteland Viper: Target attacking creature gets +1/+2 and gains deathtouch until end of turn.

Marsh Boa

Spire Winder

Flying
Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
Spire Winder gets +1/+1 as long as you have the city's blessing.

Feiyi Snake

Reach (This creature can block creatures with flying.)

Patagia Viper

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

Winged Coatl

Flash (You may cast this spell any time you could cast an instant.)
Flying
Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Zodiac Snake

Coiled Tinviper

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.)

Mold Adder

Whenever an opponent casts a blue or black spell, you may put a +1/+1 counter on this creature.

Lotus Cobra

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

Erebos's Emissary

Bestow {5}{B} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Discard a creature card: Erebos's Emissary gets +2/+2 until end of turn. If Erebos's Emissary is an Aura, enchanted creature gets +2/+2 until end of turn instead.
Enchanted creature gets +3/+3.

Orochi Sustainer

Python

Hornet Cobra

Ukud Cobra

Ramunap Hydra

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

Prowling Serpopard

This spell can't be countered.
Creature spells you control can't be countered.

Vector Asp

{B}: Vector Asp gains infect until end of turn. (It deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

Narnam Cobra

{G}: Narnam Cobra gains deathtouch until end of turn. (Any amount of damage it deals to a creature is enough to destroy it.)

Jewel-Eyed Cobra

Deathtouch
When Jewel-Eyed Cobra dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Wall of Vipers

Defender (This creature can't attack.)
{3}: Destroy Wall of Vipers and target creature it's blocking. Any player may activate this ability.

Death-Hood Cobra

{1}{G}: Death-Hood Cobra gains reach until end of turn.
{1}{G}: Death-Hood Cobra gains deathtouch until end of turn.

Gravebreaker Lamia

Lifelink
When Gravebreaker Lamia enters, search your library for a card, put it into your graveyard, then shuffle.
Spells you cast from your graveyard cost {1} less to cast.

Ambush Viper

Zagoth Mamba

Whenever this creature mutates, target creature an opponent controls gets -2/-2 until end of turn.

Hagra Constrictor

Hagra Constrictor enters with two +1/+1 counters on it.
Each creature you control with a +1/+1 counter on it has menace. (A creature with menace can't be blocked except by two or more creatures.)

Ice-Fang Coatl

Flash
Flying
When Ice-Fang Coatl enters, draw a card.
Ice-Fang Coatl has deathtouch as long as you control at least three other snow permanents.

Skeletal Crocodile

River Boa

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

Boa Constrictor

{T}: Boa Constrictor gets +3/+3 until end of turn.

Snake of the Golden Grove

Tribute 3 (As this creature enters, an opponent of your choice may put three +1/+1 counters on it.)
When Snake of the Golden Grove enters, if tribute wasn't paid, you gain 4 life.

Tangle Asp

Whenever Tangle Asp blocks or becomes blocked by a creature, destroy that creature at end of combat.

Voracious Cobra

First strike
Whenever Voracious Cobra deals combat damage to a creature, destroy that creature.

Zaxara, the Exemplary

Deathtouch
{T}: Add two mana of any one color.
Whenever you cast a spell with {X} in its mana cost, create a 0/0 green Hydra creature token, then put X +1/+1 counters on it.

Noose Constrictor

Reach
Discard a card: Noose Constrictor gets +1/+1 until end of turn.

Ribbon Snake

Flying
{2}: Ribbon Snake loses flying until end of turn. Any player may activate this ability.

Skeletal Snake

Nafs Asp

Whenever Nafs Asp deals damage to a player, that player loses 1 life at the beginning of their next draw step unless they pay {1} before that draw step.

Zombie Boa

{1}{B}: Choose a color. Whenever Zombie Boa becomes blocked by a creature of that color this turn, destroy that creature. Activate only as a sorcery.

Skullwinder

Deathtouch
When Skullwinder enters, return target card from your graveyard to your hand, then choose an opponent. That player returns a card from their graveyard to their hand.

Mire Boa

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
{G}: Regenerate Mire Boa. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Hooded Hydra

Hooded Hydra enters with X +1/+1 counters on it.
When Hooded Hydra dies, create a 1/1 green Snake creature token for each +1/+1 counter on it.
Morph {3}{G}{G}
As Hooded Hydra is turned face up, put five +1/+1 counters on it.

Glass Asp

Whenever Glass Asp deals combat damage to a player, that player loses 2 life at the beginning of their next draw step unless they pay {2} before that step.

Stonecoil Serpent

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

Ophidian Eye

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Whenever enchanted creature deals damage to an opponent, you may draw a card.

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 Broodbirth Viper deals combat damage to a player, you may draw a card.

Sabertooth Cobra

Whenever Sabertooth Cobra deals damage to a player, that player gets a poison counter. The player gets another poison counter at the beginning of their next upkeep unless they pay {2} before that step. (A player with ten or more poison counters loses the game.)

Voracious Typhon

Escape—{5}{G}{G}, Exile four other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)
Voracious Typhon escapes with three +1/+1 counters on it.