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).

Consulate Turret

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

Aetherstream Leopard

Trample
When Aetherstream Leopard enters, you get {E} (an energy counter).
Whenever Aetherstream Leopard attacks, you may pay {E}. If you do, it gets +2/+0 until end of turn.

Forest

Aether Poisoner

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
When Aether Poisoner enters, 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.

Thriving Rats

When Thriving Rats enters, 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.

Riparian Tiger

Trample
When Riparian Tiger enters, you get {E}{E} (two energy counters).
Whenever Riparian Tiger attacks, you may pay {E}{E}. If you do, it gets +2/+2 until end of turn.

Live Fast

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

Thriving Rhino

When Thriving Rhino enters, 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.

Woodweaver's Puzzleknot

When Woodweaver's Puzzleknot enters, you gain 3 life and get {E}{E}{E} (three energy counters).
{2}{G}, Sacrifice Woodweaver's Puzzleknot: You gain 3 life and get {E}{E}{E}.

Swamp

Highspire Infusion

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

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.