Voltaic Brawler

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

Bristling Hydra

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

Evolving Wilds

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

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).

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.

Mountain

Greenbelt Rampager

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

Harnessed Lightning

Choose target creature. You get {E}{E}{E} (three energy counters), then you may pay any amount of {E}. Harnessed Lightning deals that much damage to that creature.

Ketria Triome

({T}: Add {G}, {U}, or {R}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Forest

Longtusk Cub

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

Rogue Refiner

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

Island

Whirler Virtuoso

When this creature enters, you get {E}{E}{E} (three energy counters).
Pay {E}{E}{E}: Create a 1/1 colorless Thopter artifact creature token with flying.

Servant of the Conduit

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

Aether Hub

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