Aether Hub

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

Evolving Wilds

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

Bristling Hydra

When Bristling Hydra enters, 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.

Frontier Bivouac

Frontier Bivouac enters tapped.
{T}: Add {G}, {U}, or {R}.

Decisive Denial

Choose one —
• Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.)
• Counter target noncreature spell unless its controller pays {3}.

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).

Longtusk Stalker

Whenever Longtusk Stalker enters or attacks, you get {E}.
Pay {E}{E}: Longtusk Stalker perpetually gets +1/+0. You may choose a creature card in your hand. If you do, that card perpetually gets +1/+0.

Servant of the Conduit

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

Island

Voltaic Brawler

When Voltaic Brawler enters, 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.

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.

Whirler Virtuoso

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

Mountain

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.

Forest

Rogue Refiner

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