When Assaultron Dominator enters the battlefield, you get {E}{E} (two energy counters).

Whenever an artifact creature you control attacks, you may pay {E}. If you do, put your choice of a +1/+1, first strike, or trample counter on that creature.

Whenever one or more artifact creatures you control deal combat damage to a player, you get {E} (an energy counter).

Pay {E}{E}{E}: Create a tapped 3/3 colorless Robot artifact creature token.

Metalcraft -- {T}: You get {E} (an energy counter). Activate only if you control three or more artifacts.

Whenever you get one or more {E} during your turn, creatures you control get +1/+1 until end of turn.

Whenever you cast an artifact spell, you get {E} (an energy counter).

{T}, Pay {E}: Target creature gets +1/+0 and gains trample and haste until end of turn.

{T}, Pay {E}{E}{E}: Draw a card.

{T}, Pay {E}{E}{E}{E}{E}: Return target artifact card from your graveyard to the battlefield tapped.

Counter target spell. You get an amount of {E} (energy counters) equal to its mana value.

{T}: Add {C}.

{1}, {T}: You get {E} (an energy counter).

{3}, {T}, Pay X {E}, Sacrifice HELIOS One: Destroy target nonland permanent with mana value X. Activate only as a sorcery.

Vigilance, trample, haste

Whenever Liberty Prime, Recharged attacks or blocks, sacrifice it unless you pay {E}{E} (two energy counters).

{2}, {T}, Sacrifice an artifact: You get {E}{E} and draw a card.

Equipped creature gets +1/+1.

Whenever equipped creature attacks, you get {E}{E} (two energy counters).

Pay {E}{E}: Choose target creature that's blocking equipped creature. Flip a coin. If you win the flip, exile the chosen creature. Otherwise, Plasma Caster deals 1 damage to it.

Equip {2}

Whenever Rex, Cyber-Hound deals combat damage to a player, they mill two cards and you get {E}{E} (two energy counters).

Pay {E}{E}: Choose target creature card in a graveyard. Exile it with a brain counter on it. Activate only as a sorcery.

Rex has all activated abilities of all cards in exile with brain counters on them.

Robobrain War Mind's power is equal to the number of cards in your hand.

When Robobrain War Mind enters the battlefield, you get an amount of {E} (energy counters) equal to the number of artifact creatures you control.

Whenever Robobrain War Mind attacks, you may pay {E}{E}{E}. If you do, draw a card.

Haste

Whenever Synth Eradicator attacks, exile the top card of your library. You may get {E}{E} (two energy counters). If you don't, you may play that card this turn.

{T}, Pay {E}{E}{E}: Synth Eradicator deals 3 damage to any target.

When T-45 Power Armor enters the battlefield, you get {E}{E} (two energy counters).

Equipped creature gets +3/+3 and doesn't untap during its controller's untap step.

At the beginning of your upkeep, you may pay {E}. If you do, untap equipped creature, then put your choice of a menace, trample, or lifelink counter on it.

Equip {3}

When The Motherlode, Excavator enters the battlefield, choose target opponent. You get an amount of {E} (energy counters) equal to the number of nonbasic lands that player controls.

Whenever The Motherlode attacks, you may pay {E}{E}{E}{E}. When you do, destroy target nonbasic land defending player controls, and creatures that player controls without flying can't block this turn.

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)

I, II -- Tap up to one target creature and put a stun counter on it. You get {E}{E} (two energy counters).

III -- Pay any amount of {E}. If you paid one or more {E} this way, shuffle your library, then exile that many cards from the top. You may play one of those cards without paying its mana cost.