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.

Sage of Shaila's Claim

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

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).

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.

Glimmer of Genius

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

Longtusk Cub

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

Thriving Grubs

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

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.