Architect of the Untamed

Landfall — Whenever a land you control enters, you get {E} (an energy counter).
Pay eight {E}: Create a 6/6 colorless Beast artifact creature token.

Saheeli, Radiant Creator

Whenever you cast an Artificer or artifact spell, you get {E} (an energy counter).
At the beginning of combat on your turn, you may pay {E}{E}{E}. When you do, create a token that's a copy of target permanent you control, except it's a 5/5 artifact creature in addition to its other types and has haste. Sacrifice it at the beginning of the next end step.

Lightning Runner

Double strike, haste
Whenever this creature attacks, you get {E}{E} (two energy counters), then you may pay eight {E}. If you pay, untap all creatures you control, and after this phase, there is an additional combat phase.

Roil Cartographer

Landfall — Whenever a land you control enters, you get {E} (an energy counter).
{T}, Pay six {E}: Draw three cards.

Pia Nalaar, Chief Mechanic

Whenever one or more artifact creatures you control deal combat damage to a player, you get {E}{E} (two energy counters).
At the beginning of your end step, you may pay one or more {E}. If you do, create an X/X colorless Vehicle artifact token named Nalaar Aetherjet with flying and crew 2, where X is the amount of {E} paid this way.

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.

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).