Gonti's Aether Heart

Whenever Gonti's Aether Heart or another artifact enters the battlefield under your control, you get {E}{E} (two energy counters).
Pay {E}{E}{E}{E}{E}{E}{E}{E}, Exile Gonti's Aether Heart: Take an extra turn after this one.

Aether Herder

When Aether Herder enters the battlefield, you get {E}{E} (two energy counters).
Whenever Aether Herder attacks, you may pay {E}{E}. If you do, create a 1/1 colorless Servo artifact creature token.

Putrefy

Destroy target artifact or creature. It can't be regenerated.

Aetherwind Basker

Trample
Whenever Aetherwind Basker enters the battlefield or attacks, you get {E} (an energy counter) for each creature you control.
Pay {E}: Aetherwind Basker gets +1/+1 until end of turn.

Highspire Infusion

Target creature gets +3/+3 until end of turn. You get {E}{E} (two energy counters).

Swamp

Shielded Aether Thief

Flash (You may cast this spell any time you could cast an instant.)
Whenever Shielded Aether Thief blocks, you get {E} (an energy counter).
{T}, Pay {E}{E}{E}: Draw a card.

Solemn Simulacrum

When Solemn Simulacrum enters the battlefield, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
When Solemn Simulacrum dies, you may draw a card.

Era of Innovation

Whenever an artifact or Artificer enters the battlefield under your control, you may pay {1}. If you do, you get {E}{E} (two energy counters).
Pay {E}{E}{E}{E}{E}{E}, Sacrifice Era of Innovation: Draw three cards.

Eternal Witness

When Eternal Witness enters the battlefield, you may return target card from your graveyard to your hand.

Fabrication Module

Whenever you get one or more {E} (energy counters), put a +1/+1 counter on target creature you control.
{4}, {T}: You get {E}.

Aether Poisoner

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
When Aether Poisoner enters the battlefield, you get {E}{E} (two energy counters).
Whenever Aether Poisoner attacks, you may pay {E}{E}. If you do, create a 1/1 colorless Servo artifact creature token.

Reservoir Walker

When Reservoir Walker enters the battlefield, you gain 3 life and get {E}{E}{E} (three energy counters).

Shipwreck Moray

When Shipwreck Moray enters the battlefield, you get {E}{E}{E}{E} (four energy counters).
Pay {E}: Shipwreck Moray gets +2/-2 until end of turn.

Coiling Oracle

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.

Architect of the Untamed

Landfall — Whenever a land enters the battlefield under your control, you get {E} (an energy counter).
Pay {E}{E}{E}{E}{E}{E}{E}{E}: Create a 6/6 colorless Beast artifact creature token.

Thassa, Deep-Dwelling

Indestructible
As long as your devotion to blue is less than five, Thassa isn't a creature.
At the beginning of your end step, exile up to one other target creature you control, then return that card to the battlefield under your control.
{3}{U}: Tap another target creature.

Aether Swooper

Flying
When Aether Swooper enters the battlefield, you get {E}{E} (two energy counters).
Whenever Aether Swooper attacks, you may pay {E}{E}. If you do, create a 1/1 colorless Servo artifact creature token.

Yarok, the Desecrated

Deathtouch, lifelink
If a permanent entering the battlefield causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Ravenous Chupacabra

When Ravenous Chupacabra enters the battlefield, destroy target creature an opponent controls.

Wood Elves

When Wood Elves enters the battlefield, search your library for a Forest card, put that card onto the battlefield, then shuffle.

Thriving Turtle

When Thriving Turtle enters the battlefield, you get {E}{E} (two energy counters).
Whenever Thriving Turtle attacks, you may pay {E}{E}. If you do, put a +1/+1 counter on it.

Sage of Shaila's Claim

When Sage of Shaila's Claim enters the battlefield, you get {E}{E}{E} (three energy counters).

Vorinclex, Monstrous Raider

Trample, haste
If you would put one or more counters on a permanent or player, put twice that many of each of those kinds of counters on that permanent or player instead.
If an opponent would put one or more counters on a permanent or player, they put half that many of each of those kinds of counters on that permanent or player instead, rounded down.

Evolution Sage

Landfall — Whenever a land enters the battlefield under your control, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Thriving Rhino

When Thriving Rhino enters the battlefield, you get {E}{E} (two energy counters).
Whenever Thriving Rhino attacks, you may pay {E}{E}. If you do, put a +1/+1 counter on it.

Cyclonic Rift

Return target nonland permanent you don't control to its owner's hand.
Overload {6}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Illusionist's Stratagem

Exile up to two target creatures you control, then return those cards to the battlefield under their owner's control.
Draw a card.

Forest

Growth Spiral

Draw a card. You may put a land card from your hand onto the battlefield.

Glint-Sleeve Siphoner

Menace
Whenever Glint-Sleeve Siphoner enters the battlefield or attacks, you get {E} (an energy counter).
At the beginning of your upkeep, you may pay {E}{E}. If you do, you draw a card and you lose 1 life.

Ghostly Flicker

Exile two target artifacts, creatures, and/or lands you control, then return those cards to the battlefield under your control.

Servant of the Conduit

When Servant of the Conduit enters the battlefield, you get {E}{E} (two energy counters).
{T}, Pay {E}: Add one mana of any color.

Die Young

Choose target creature. You get {E}{E} (two energy counters), then you may pay any amount of {E}. The creature gets -1/-1 until end of turn for each {E} paid this way.

Rogue Refiner

When Rogue Refiner enters the battlefield, draw a card and you get {E}{E} (two energy counters).

Janjeet Sentry

When Janjeet Sentry enters the battlefield, you get {E}{E} (two energy counters).
{T}, Pay {E}{E}: You may tap or untap target artifact or creature.

Farhaven Elf

When Farhaven Elf enters the battlefield, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Krosan Grip

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Destroy target artifact or enchantment.

Demon of Dark Schemes

Flying
When Demon of Dark Schemes enters the battlefield, all other creatures get -2/-2 until end of turn.
Whenever another creature dies, you get {E} (an energy counter).
{2}{B}, Pay {E}{E}{E}{E}: Put target creature card from a graveyard onto the battlefield under your control tapped.

Live Fast

You draw two cards, lose 2 life, and get {E}{E} (two energy counters).

Minister of Inquiries

When Minister of Inquiries enters the battlefield, you get {E}{E} (two energy counters).
{T}, Pay {E}: Target player mills three cards.

Thriving Rats

When Thriving Rats enters the battlefield, you get {E}{E} (two energy counters).
Whenever Thriving Rats attacks, you may pay {E}{E}. If you do, put a +1/+1 counter on it.

Mulldrifter

Flying
When Mulldrifter enters the battlefield, draw two cards.
Evoke {2}{U} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters the battlefield.)

Attune with Aether

Search your library for a basic land card, reveal it, put it into your hand, then shuffle. You get {E}{E} (two energy counters).

Reclamation Sage

When Reclamation Sage enters the battlefield, you may destroy target artifact or enchantment.

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Island

Decoction Module

Whenever a creature enters the battlefield under your control, you get {E} (an energy counter).
{4}, {T}: Return target creature you control to its owner's hand.

Empyreal Voyager

Flying, trample
Whenever Empyreal Voyager deals combat damage to a player, you get that many {E} (energy counters).

Glimmer of Genius

Scry 2, then draw two cards. You get {E}{E} (two energy counters).

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Counterspell

Peema Aether-Seer

When Peema Aether-Seer enters the battlefield, you get an amount of {E} (energy counters) equal to the greatest power among creatures you control.
Pay {E}{E}{E}: Target creature blocks this turn if able.

Confiscation Coup

Choose target artifact or creature. You get {E}{E}{E}{E} (four energy counters), then you may pay an amount of {E} equal to that permanent's mana value. If you do, gain control of it.

Acidic Slime

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
When Acidic Slime enters the battlefield, destroy target artifact, enchantment, or land.

Displace

Exile up to two target creatures you control, then return those cards to the battlefield under their owner's control.

Electrostatic Pummeler

When Electrostatic Pummeler enters the battlefield, you get {E}{E}{E} (three energy counters).
Pay {E}{E}{E}: Electrostatic Pummeler gets +X/+X until end of turn, where X is its power.

Thrummingbird

Flying
Whenever Thrummingbird deals combat damage to a player, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Aethersquall Ancient

Flying
At the beginning of your upkeep, you get {E}{E}{E} (three energy counters).
Pay {E}{E}{E}{E}{E}{E}{E}{E}: Return all other creatures to their owners' hands. Activate only as a sorcery.

Aetherworks Marvel

Whenever a permanent you control is put into a graveyard, you get {E} (an energy counter).
{T}, Pay {E}{E}{E}{E}{E}{E}: Look at the top six cards of your library. You may cast a spell from among them without paying its mana cost. Put the rest on the bottom of your library in a random order.

Greenbelt Rampager

When Greenbelt Rampager enters the battlefield, pay {E}{E} (two energy counters). If you can't, return Greenbelt Rampager to its owner's hand and you get {E}.

Steady Progress

Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
Draw a card.

Multiform Wonder

When Multiform Wonder enters the battlefield, you get {E}{E}{E} (three energy counters).
Pay {E}: Multiform Wonder gains your choice of flying, vigilance, or lifelink until end of turn.
Pay {E}: Multiform Wonder gets +2/-2 or -2/+2 until end of turn.

Teferi's Time Twist

Exile target permanent you control. Return that card to the battlefield under its owner's control at the beginning of the next end step. If it enters the battlefield as a creature, it enters with an additional +1/+1 counter on it.

Heroic Intervention

Permanents you control gain hexproof and indestructible until end of turn.

Longtusk Cub

Whenever Longtusk Cub deals combat damage to a player, you get {E}{E} (two energy counters).
Pay {E}{E}: Put a +1/+1 counter on Longtusk Cub.

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.

Aethertide Whale

Flying
When Aethertide Whale enters the battlefield, you get {E}{E}{E}{E}{E}{E} (six energy counters).
Pay {E}{E}{E}{E}: Return Aethertide Whale to its owner's hand.

Aether Theorist

When Aether Theorist enters the battlefield, you get {E}{E}{E} (three energy counters).
{T}, Pay {E}: Scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Bristling Hydra

When Bristling Hydra enters the battlefield, you get {E}{E}{E} (three energy counters).
Pay {E}{E}{E}: Put a +1/+1 counter on Bristling Hydra. It gains hexproof until end of turn.

Roalesk, Apex Hybrid

Flying, trample
When Roalesk, Apex Hybrid enters the battlefield, put two +1/+1 counters on another target creature you control.
When Roalesk dies, proliferate, then proliferate again. (Choose any number of permanents and/or players, then give each another counter of each kind already there. Then do it again.)