Lathnu Hellion

Haste
When this creature enters, you get {E}{E} (two energy counters).
At the beginning of your end step, sacrifice this creature unless you pay {E}{E}.

Aether Refinery

If you would get one or more {E} (energy counters), you get twice that many {E} instead.
{T}: You get {E}, then you may pay one or more {E}. If you do, create an X/X black Aetherborn creature token, where X is the amount of {E} paid this way.

Thriving Skyclaw

Flying
When this creature enters, you get {E}{E}{E} (three energy counters).
Whenever this creature attacks, you may pay {E}{E}{E}. If you do, put a +1/+1 counter on it.

Phyrexian Ironworks

Whenever you attack, you get {E} (an energy counter).
{T}, Pay {E}{E}{E}: Create a 3/3 colorless Phyrexian Golem artifact creature token. Activate only as a sorcery.

Lightning Runner

Double strike, haste
Whenever this creature attacks, you get {E}{E} (two energy counters), then you may pay eight {E}. If you pay, untap all creatures you control, and after this phase, there is an additional combat phase.

Smelted Chargebug

Menace
When this creature enters, you get {E}{E} (two energy counters).
Whenever this creature attacks, you may pay {E}. If you do, another target attacking creature gets +1/+0 and gains menace until end of turn.

Electrostatic Pummeler

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

Conversion Apparatus

{T}: Add {C}.
{3}, {T}: You get {E}{E}{E} (three energy counters).
{T}, Pay {E}{E}{E}: Add three mana in any combination of colors.

Amped Raptor

First strike
When this creature enters, you get {E}{E} (two energy counters). Then if you cast it from your hand, exile cards from the top of your library until you exile a nonland card. You may cast that card by paying an amount of {E} equal to its mana value rather than paying its mana cost.

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.

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.

Scrapper Champion

Double strike (This creature deals both first-strike and regular combat damage.)
When this creature enters, you get {E}{E} (two energy counters).
Whenever this creature attacks, you may pay {E}{E}. If you do, put a +1/+1 counter on it.

Stone Idol Generator

Whenever a creature you control attacks, you get {E} (an energy counter).
{T}, Pay six {E}: Create a 6/12 colorless Construct artifact creature token with trample. Activate only as a sorcery.

Aether Chaser

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

HELIOS One

{T}: Add {C}.
{1}, {T}: You get {E} (an energy counter).
{3}, {T}, Pay X {E}, Sacrifice this land: Destroy target nonland permanent with mana value X. Activate only as a sorcery.

Reservoir Walker

When this creature enters, you gain 3 life and get {E}{E}{E} (three energy counters).

Behemoth of Vault 0

Trample
When this creature enters, you get {E}{E}{E}{E} (four energy counters).
When this creature dies, you may pay an amount of {E} equal to target nonland permanent's mana value. When you do, destroy that permanent.

Aethertorch Renegade

When this creature enters, you get {E}{E}{E}{E} (four energy counters).
{T}, Pay {E}{E}: This creature deals 1 damage to target creature.
{T}, Pay eight {E}: This creature deals 6 damage to target player or planeswalker.

Aether Hub

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

Thriving Grubs

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

Consulate Turret

{T}: You get {E} (an energy counter).
{T}, Pay {E}{E}{E}: This artifact deals 2 damage to target player or planeswalker.

Galvanic Discharge

Choose target creature or planeswalker. You get {E}{E}{E} (three energy counters), then you may pay any amount of {E}. Galvanic Discharge deals that much damage to that permanent.

The Motherlode, Excavator

When The Motherlode enters, choose target opponent. You get an amount of {E} (energy counters) equal to the number of nonbasic lands that player controls.
Whenever The Motherlode attacks, you may pay {E}{E}{E}{E}. When you do, destroy target nonbasic land defending player controls, and creatures that player controls without flying can't block this turn.

Multiform Wonder

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

Assaultron Dominator

When this creature enters, you get {E}{E} (two energy counters).
Whenever an artifact creature you control attacks, you may pay {E}. If you do, put your choice of a +1/+1, first strike, or trample counter on that creature.

Blaster Hulk

This spell costs {1} less to cast for each {E} (energy counter) you've paid or lost this turn.
Haste
Whenever this creature attacks, you get {E}{E}, then you may pay eight {E}. When you do, this creature deals 8 damage divided as you choose among up to eight targets.

Dynavolt Tower

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

Maulfist Doorbuster

When this creature enters, you get {E}{E} (two energy counters).
Whenever this creature attacks, you may pay {E}. If you do, target creature can't block this turn.

Solar Transformer

This artifact enters tapped.
When this artifact enters, you get {E}{E}{E} (three energy counters).
{T}: Add {C}.
{T}, Pay {E}: Add one mana of any color.

Wheel of Potential

You get {E}{E}{E} (three energy counters), then you may pay any amount of {E}.
Each player may exile their hand and draw a number of cards equal to the amount of {E} paid this way. If seven or more {E} was paid this way, you may play cards you own exiled this way until the end of your next turn.

Synth Eradicator

Haste
Whenever this creature attacks, exile the top card of your library. You may get {E}{E} (two energy counters). If you don't, you may play that card this turn.
{T}, Pay {E}{E}{E}: This creature deals 3 damage to any target.