Gonti's Aether Heart

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

Tezzeret's Gambit

({U/P} can be paid with either {U} or 2 life.)
Draw two cards, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Aetherworks Marvel

Whenever a permanent you control is put into a graveyard, you get {E} (an energy counter).
{T}, Pay six {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.

Glint-Sleeve Siphoner

Menace
Whenever Glint-Sleeve Siphoner enters 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.

Dimir Signet

Dynavolt Tower

Whenever you cast an instant or sorcery spell, you get {E}{E} (two energy counters).
{T}, Pay {E}{E}{E}{E}{E}: Dynavolt Tower deals 3 damage to any target.

Live Fast

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

Aetherwind Basker

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

Arcane Signet

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

Golgari Signet

Peema Aether-Seer

When Peema Aether-Seer enters, 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.

Island

Empyreal Voyager

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

Forest

Sol Ring

Aethertide Whale

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

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).

Aether Hub

When Aether Hub enters, you get {E} (an energy counter).
{T}: Add {C}.
{T}, Pay {E}: Add one mana of any color.

Riftsweeper

When Riftsweeper enters, choose target face-up exiled card. Its owner shuffles it into their library.

Conjurer's Closet

At the beginning of your end step, you may exile target creature you control, then return that card to the battlefield under your control.

Yarok, the Desecrated

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

Glassblower's Puzzleknot

When Glassblower's Puzzleknot enters, scry 2, then you get {E}{E}. (You get two energy counters. To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)
{2}{U}, Sacrifice Glassblower's Puzzleknot: Scry 2, then you get {E}{E}.

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.

Simic Signet

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.

Glimmer of Genius

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

Evolution Sage

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

Deadlock Trap

Deadlock Trap enters tapped.
When Deadlock Trap enters, you get {E}{E} (two energy counters).
{T}, Pay {E}: Tap target creature or planeswalker. Its activated abilities can't be activated this turn.

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.

Janjeet Sentry

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

Electrostatic Pummeler

When Electrostatic Pummeler enters, 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.

Command Tower

Bristling Hydra

When Bristling Hydra enters, 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.

Rogue Refiner

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

Servant of the Conduit

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

Sage of Shaila's Claim

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

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}.

Panharmonicon

If an artifact or creature entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Flux Channeler

Whenever you cast a noncreature spell, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Animation Module

Whenever one or more +1/+1 counters are put on a permanent you control, you may pay {1}. If you do, create a 1/1 colorless Servo artifact creature token.
{3}, {T}: Choose a counter on target permanent or player. Give that permanent or player another counter of that kind.

Aethersquall Ancient

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

Demon of Dark Schemes

Flying
When Demon of Dark Schemes enters, 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.

Decimator Web

{4}, {T}: Target opponent loses 2 life, gets a poison counter, then mills six cards.

Gonti's Machinations

Whenever you lose life for the first time each turn, you get {E}. (You get an energy counter. Damage causes loss of life.)
Pay {E}{E}, Sacrifice Gonti's Machinations: Each opponent loses 3 life. You gain life equal to the life lost this way.

Swamp

Decoction Module

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

Era of Innovation

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

Architect of the Untamed

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

Aether Theorist

When Aether Theorist enters, 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.)