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 the battlefield, you get {E} (an energy counter).
{T}: Add {C}.
{T}, Pay {E}: Add one mana of any color.

Lathnu Hellion

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

Sage of Shaila's Claim

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

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.

Forest

Mountain

Built to Smash

Target attacking creature gets +3/+3 until end of turn. If it's an artifact creature, it gains trample until end of turn.

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.

Uncaged Fury

Target creature gets +1/+1 and gains double strike until end of turn. (It deals both first-strike and regular combat damage.)

Larger Than Life

Target creature gets +4/+4 and gains trample until end of turn.

Blossoming Defense

Target creature you control gets +2/+2 and gains hexproof until end of turn.

Voltaic Brawler

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

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.