You may have Altered Ego enter the battlefield as a copy of any creature on the battlefield, except it enters with X additional +1/+1 counters on it.
0 /
0
{2}{G}
Arachnogenesis
Instant
Create X 1/2 green Spider creature tokens with reach, where X is the number of creatures attacking you. Prevent all combat damage that would be dealt this turn by non-Spider creatures.
{2}{U}
Arcane Adaptation
Enchantment
As Arcane Adaptation enters the battlefield, choose a creature type.
Creatures you control are the chosen type in addition to their other types. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.
{2}{G}
Beast Within
Instant
Destroy target permanent. Its controller creates a 3/3 green Beast creature token.
{2}{G}
Beastmaster Ascension
Enchantment
Whenever a creature you control attacks, you may put a quest counter on Beastmaster Ascension.
As long as Beastmaster Ascension has seven or more quest counters on it, creatures you control get +5/+5.
{2}{U}{U}
Bident of Thassa
Legendary Enchantment Artifact
Whenever a creature you control deals combat damage to a player, you may draw a card.
{1}{U}, {T}: Creatures your opponents control attack this turn if able.
{X}{G/U}{G/U}
Biomass Mutation
Instant
Creatures you control have base power and toughness X/X until end of turn.
{1}{G}
Blight Mamba
Creature - Phyrexian Snake
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.
1 /
1
{4}{U}
Broodbirth Viper
Creature - Snake
Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token that's a copy of this creature 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.
3 /
3
{2}{G}{G}
Chameleon Colossus
Creature - Shapeshifter
Changeling (This card is every creature type.)
Protection from black
{2}{G}{G}: Chameleon Colossus gets +X/+X until end of turn, where X is its power.
4 /
4
{4}{G}{G}
Cobra Trap
Instant - 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.
{G}{U}
Coiling Oracle
Creature - Snake Elf Druid
When Coiling Oracle enters the battlefield, 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.
1 /
1
--
Command Tower
Land
{T}: Add one mana of any color in your commander's color identity.
{3}
Commander's Sphere
Artifact
{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.
{U}{U}
Counterspell
Instant
Counter target spell.
{2}{G}
Cultivate
Sorcery
Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.
{1}{G}{U}
Edric, Spymaster of Trest
Legendary Creature - Elf Rogue
Whenever a creature deals combat damage to one of your opponents, its controller may draw a card.
2 /
2
--
Evolving Wilds
Land
{T}, Sacrifice Evolving Wilds: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
{3}{G}
Explosive Vegetation
Sorcery
Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.
{5}{G}{G}{G}
Ezuri's Predation
Sorcery
For each creature your opponents control, create a 4/4 green Phyrexian Beast creature token. Each of those tokens fights a different one of those creatures.
{3}
Fireshrieker
Artifact - Equipment
Equipped creature has double strike. (It deals both first-strike and regular combat damage.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
{4}
Grafted Exoskeleton
Artifact - Equipment
Equipped creature gets +2/+2 and has infect. (It deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
Whenever Grafted Exoskeleton becomes unattached from a permanent, sacrifice that permanent.
Equip {2}
{2}{G}{G}
Harmonize
Sorcery
Draw three cards.
{5}{G}
Honored Hydra
Creature - Snake 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.)
6 /
6
{X}{G}{G}
Hooded Hydra
Creature - Snake Hydra
Hooded Hydra enters the battlefield 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.
0 /
0
{4}{U}
Illusory Ambusher
Creature - Cat Illusion
Flash (You may cast this spell any time you could cast an instant.)
Whenever Illusory Ambusher is dealt damage, draw that many cards.
4 /
1
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
{1}{G}{U}
Kaseto, Orochi Archmage
Legendary Creature - Snake Wizard
{G}{U}: Target creature can't be blocked this turn. If that creature is a Snake, it gets +2/+2 until end of turn.
2 /
2
{2}{G}
Kodama's Reach
Sorcery - Arcane
Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.
{1}{G}{U}
Lorescale Coatl
Creature - Snake
Whenever you draw a card, put a +1/+1 counter on Lorescale Coatl.
2 /
2
--
Lumbering Falls
Land
Lumbering Falls enters the battlefield tapped.
{T}: Add {G} or {U}.
{2}{G}{U}: Lumbering Falls becomes a 3/3 green and blue Elemental creature with hexproof until end of turn. It's still a land.
{3}{G}
Marsh Viper
Creature - Snake
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.)
1 /
2
{2}{G/U}{G/U}{G/U}
Murkfiend Liege
Creature - Horror
Other green creatures you control get +1/+1.
Other blue creatures you control get +1/+1.
Untap all green and/or blue creatures you control during each other player's untap step.
4 /
4
--
Myriad Landscape
Land
Myriad Landscape enters the battlefield tapped.
{T}: Add {C}.
{2}, {T}, Sacrifice Myriad Landscape: Search your library for up to two basic land cards that share a land type, put them onto the battlefield tapped, then shuffle.
{1}{G}{U}{U}
Mystic Snake
Creature - Snake
Flash
When Mystic Snake enters the battlefield, counter target spell.
2 /
2
{1}{G}
Naturalize
Instant
Destroy target artifact or enchantment.
--
Novijen, Heart of Progress
Land
{T}: Add {C}.
{G}{U}, {T}: Put a +1/+1 counter on each creature that entered the battlefield this turn.
{6}
Obelisk of Urd
Artifact
Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
As Obelisk of Urd enters the battlefield, choose a creature type.
Creatures you control of the chosen type get +2/+2.
{1}{G}{G}
Ohran Viper
Snow Creature - Snake
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.
1 /
3
{2}{G}
Orochi Eggwatcher
Creature - Snake Shaman
{2}{G}, {T}: Create a 1/1 green Snake creature token. If you control ten or more creatures, flip Orochi Eggwatcher.
1 /
1
--
Shidako, Broodmistress
Legendary Creature - Snake Shaman
{G}, Sacrifice a creature: Target creature gets +3/+3 until end of turn.
1 /
1
{X}{X}
Orochi Hatchery
Artifact
Orochi Hatchery enters the battlefield with X charge counters on it.
{5}, {T}: Create a 1/1 green Snake creature token for each charge counter on Orochi Hatchery.
{G}
Orochi Leafcaller
Creature - Snake Shaman
{G}: Add one mana of any color.
1 /
1
{1}{G}
Orochi Sustainer
Creature - Snake Shaman
{T}: Add {G}.
1 /
2
{1}{U}
Plaxmanta
Creature - Beast
Flash
When Plaxmanta enters the battlefield, creatures you control gain shroud until end of turn. (They can't be the targets of spells or abilities.)
When Plaxmanta enters the battlefield, sacrifice it unless {G} was spent to cast it.
2 /
2
{3}{G}{G}
Primal Command
Sorcery
Choose two --
• Target player gains 7 life.
• Put target noncreature permanent on top of its owner's library.
• Target player shuffles their graveyard into their library.
• Search your library for a creature card, reveal it, put it into your hand, then shuffle.
{1}{G}
Rampant Growth
Sorcery
Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
{U}
Rapid Hybridization
Instant
Destroy target creature. It can't be regenerated. That creature's controller creates a 3/3 green Frog Lizard creature token.
{2}{G}
Sabertooth Cobra
Creature - Snake
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.)
2 /
2
{4}{G}{G}
Sakiko, Mother of Summer
Legendary Creature - Snake Shaman
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.
3 /
3
{1}{G}
Sakura-Tribe Elder
Creature - Snake Shaman
Sacrifice Sakura-Tribe Elder: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
1 /
1
{G}
Sakura-Tribe Scout
Creature - Snake Shaman Scout
{T}: You may put a land card from your hand onto the battlefield.
1 /
1
{3}{G}
Sakura-Tribe Springcaller
Creature - Snake Shaman
At the beginning of your upkeep, add {G}. Until end of turn, you don't lose this mana as steps and phases end.
2 /
4
{4}{G}{G}
Seshiro the Anointed
Legendary Creature - Snake Monk
Other Snake creatures you control get +2/+2.
Whenever a Snake you control deals combat damage to a player, you may draw a card.
3 /
4
{3}{G}
Shisato, Whispering Hunter
Legendary Creature - Snake Warrior
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.
2 /
2
{G}{U}
Simic Charm
Instant
Choose one --
• Target creature gets +3/+3 until end of turn.
• Permanents you control gain hexproof until end of turn.
• Return target creature to its owner's hand.
--
Simic Growth Chamber
Land
Simic Growth Chamber enters the battlefield tapped.
When Simic Growth Chamber enters the battlefield, return a land you control to its owner's hand.
{T}: Add {G}{U}.
--
Simic Guildgate
Land - Gate
Simic Guildgate enters the battlefield tapped.
{T}: Add {G} or {U}.
{3}
Simic Keyrune
Artifact
{T}: Add {G} or {U}.
{G}{U}: Simic Keyrune becomes a 2/3 green and blue Crab artifact creature with hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)
{2}
Simic Signet
Artifact
{1}, {T}: Add {G}{U}.
{2}{G}
Skullwinder
Creature - Snake
Deathtouch
When Skullwinder enters the battlefield, return target card from your graveyard to your hand, then choose an opponent. That player returns a card from their graveyard to their hand.
1 /
3
{2}{G/U}
Snakeform
Instant
Until end of turn, target creature loses all abilities and becomes a green Snake with base power and toughness 1/1.
Draw a card.
{1}
Sol Ring
Artifact
{T}: Add {C}{C}.
{2}{G}
Sosuke's Summons
Sorcery
Create two 1/1 green Snake creature tokens.
Whenever a nontoken Snake enters the battlefield under your control, you may return Sosuke's Summons from your graveyard to your hand.
{2}{G}{G}
Sosuke, Son of Seshiro
Legendary Creature - Snake Warrior
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.
3 /
4
{3}{U}{U}
Spell Swindle
Instant
Counter target spell. Create X Treasure tokens, where X is that spell's mana value. (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")
{2}
Swiftfoot Boots
Artifact - Equipment
Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}
--
Terramorphic Expanse
Land
{T}, Sacrifice Terramorphic Expanse: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
--
Thornwood Falls
Land
Thornwood Falls enters the battlefield tapped.
When Thornwood Falls enters the battlefield, you gain 1 life.
{T}: Add {G} or {U}.
{4}{G}{G}
Thunderfoot Baloth
Creature - Beast
Trample
Lieutenant -- As long as you control your commander, Thunderfoot Baloth gets +2/+2 and other creatures you control get +2/+2 and have trample.
5 /
5
{1}{G}
Time of Need
Sorcery
Search your library for a legendary creature card, reveal it, put it into your hand, then shuffle.
{2}{G}{G}
Triumph of the Hordes
Sorcery
Until end of turn, creatures you control get +1/+1 and gain trample and infect. (Creatures with infect deal damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
{5}
Vanquisher's Banner
Artifact
As Vanquisher's Banner enters the battlefield, choose a creature type.
Creatures you control of the chosen type get +1/+1.
Whenever you cast a creature spell of the chosen type, draw a card.
--
Vivid Creek
Land
Vivid Creek enters the battlefield tapped with two charge counters on it.
{T}: Add {U}.
{T}, Remove a charge counter from Vivid Creek: Add one mana of any color.
--
Vivid Grove
Land
Vivid Grove enters the battlefield tapped with two charge counters on it.
{T}: Add {G}.
{T}, Remove a charge counter from Vivid Grove: Add one mana of any color.
{1}{G}{U}
Winged Coatl
Creature - Snake
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.)
1 /
1
--
Woodland Stream
Land
Woodland Stream enters the battlefield tapped.
{T}: Add {G} or {U}.
--
Yavimaya Coast
Land
{T}: Add {C}.
{T}: Add {G} or {U}. Yavimaya Coast deals 1 damage to you.