Epsilon

"I will not run from this fight. For I know that this bridge must be crossed to achieve our ideal. They will tremble before the power of Epsilon!"

- Epsilon

Epsilon, known as Ipsilon (イプシロン) in Japan, is the "Unknown Energy Manipulator: Test Model" from Mega Man X: Command Mission. He serves as the leader of the Rebellion Army and acts as the game's antagonist up until the final chapter.

Characteristics
Epsilon is a large Reploid, standing taller and broader than any of his cadres. He has dark skin and eyes. His body is covered in black and red armor, and wild tangled wires reach out from his arms and back. His helmet and shoulderpads have several rods protruding out of them, and he has an orange visor that covers his eyes. He normally wears a tattered black cloak, which covers most of his body and makes the mess of wires on his back appear as dark wings of some sort.

Epsilon is a well-intentioned extremist who truly believes that what he's doing is right and does not see himself as a villain. A proud and noble individual, Epsilon is often seen standing silently, his stoic nature creating a strong presence. He is deeply respected by his followers due to his ambition, wisdom, and poise. Epsilon somehow retained his sanity from the Supra-Force Metal experiments of his past, and now desires to give power to other Reploids using Supra-Force Metal as well - without driving them insane. He believes that Reploids can evolve past what humans have made them to be, and will do whatever it takes to make others realize this goal as well. This goal of seeking Reploid evolution is similar to Sigma's; Epsilon's name and motif share similarities with Sigma in general, as both are large, visionary Reploids named after a letter of the Greek alphabet. However, Epsilon does not share Sigma's genocidal aggression against humans.

Creation
While exploring the Lagrano Ruins, X can find a pod used during Epsilon's development. His pod details that he was the only Reploid to survive the Supra-Force Metal infusion experiments, giving him heightened intelligence and strength capabilities. All other volunteers in the experiment either went mad (Maverick) or perished outright.

Mega Man X: Command Mission
Before the story, Epsilon masterminded the revolt in Giga City and became the leader of the Rebellion Army's plans. This disturbance causes the Maverick Hunters to deploy X, Zero, and Shadow to the island for an investigation. However, Epsilon manages to turn Shadow to his side before the mission and gets him to lead X and Zero into an ambush with the rest of the cadres. Epsilon tries to convince the two Hunters to join his cause, but they both refuse and escape, albeit separated. Although Ferham wants to give pursuit, Epsilon orders her to stand down.

Throughout the rest of the game, Epsilon makes attempts to control Giga City's resources while crushing the Resistance that opposes him. Realizing he needs force to make others listen to his ideals, he resorts to creating a missile armed with Supra-Force Metal to keep his foes at bay. He directly orders his cadres to carry out these missions on multiple occasions. Eventually, X and his team trace Scarface's location, leading them to Epsilon's hideout in the Grave Ruins Base. Epsilon is prepared to fight them, but Scarface takes his place, urging him to flee. After Scarface falls in his name, Epsilon refuses to run away and takes them on himself, only to lose. He then states that his options for achieving his goal were very limited, due to his group being labeled Mavericks so quickly. As he tries to continue fighting, X brings him down with his buster.

After the end of the game, Epsilon was deferred of all Maverick charges posthumously, most likely due to the restraint he showed in not killing innocents (having banished the humans from Giga City without harm, simply forbidding them to return), and the fact that his whole Maverick status came about as a result of the traitorous Redips' command.

Round 2
As a result of Supra-Force Metal testing, Epsilon is extraordinarily strong and durable, as it took six Reploids to take him down. Using his implanted Supra-Force Metal grants him even more devastating attacks, as well as alternating resistance to Combat and Shot attacks and regeneration capabilities until his Supra-Force Metal output has been weakened by damage. Epsilon's second phase is called Eject Epsilon, having his restraints removed and his Supra-Force Metal output slightly boosted.

Grave Ruins Base
(Maverick Hunters X and Zero make it to the top on the Grave Ruins Base and run in to confront the Rebellion Army's leader, Epsilon.)

Zero: Hah! Epsilon.

X: It's game over! For your plans, and your Rebellion!

(Epsilon stands, towering over the two Hunters.)

Epsilon: So, the Maverick Hunters have arrived. If you think you've declawed us by securing the missile's Force Metal, you're terribly wrong!

Zero: What?!

(Epsilon hold his left hand against his chest.)

Epsilon: We still have Supra-Force Metal here! After we dispose of you, we'll use it in the warhead!

(X begins charging up.)

X: I don't think so. Not if we have anything to say about it!

(X fires a fully charged blast, but at the last second, Scarface leaps in the way and absorbs the blast.)

Epsilon: Scarface!

Scarface: Commander, please leave this to me. That rat, X... he learns new powers as he fights. If you were to somehow lose this fight, where would we be then?!

Epsilon: Out of the way, Scarface! Or are you suggesting I would lose?

Scarface: You alone carry the Rebellion Army torch! Commander Epsilon, you are the embodiment of our beliefs! Make the choice to live another day!

Zero: We won't let you get away, Epsilon! Your fun and games have come to an end!

(Scarface turns to face the Hunters again.)

Scarface: I beseech you, Commander... Allow me to demonstrate the depth of my faith!

(Scarface proceeds to battle with the Hunters again, only to lose a second time.)

(In his last breath Scarface raises his arm in honor for the Rebellion Army.)

Scarface: Glory to the Rebellion!

(Scarface coughs one last time before exploding. Epsilon looks down upon his fallen bodyguard, then glares at the Hunters.)

Epsilon: I can see you are determined. But Scarface... I will not run from this fight. For I know that this bridge must be crossed to achieve our ideal.

(Epsilon steps forward in a battle stance.)

Epsilon: They will tremble before the power of... Epsilon!

(The Hunters engage Epsilon in battle.)

(After the battle, Epsilon crouches near the ground, terribly wounded. X continues to keep his Buster trained on him.)

X: Why?! Why create something as dangerous as the Supra-Force Metal missile?!

Epsilon: For power. Without power... our ideas will be ignored.

X: What?! There must be a better way...

Epsilon: The Federation has labeled us Maverick. What other options do we have?!

(Epsilon climbs to his feet.)

Epsilon: As long as I am in operation, I will...

Zero: Now, X... shoot!!

(X fires his final blast at Epsilon, this time bringing him down for good. X approaches and retrieves the Supra-Force Metal Epsilon had been using.)

X: So this is Epsilon's Supra-Force Metal?

Zero: Despite all their big talk, the Rebellion Army's actions were still Maverick.

Axl: They put the Earth itself at risk.

Zero: We did the right thing.

(From behind, Colonel Redips approaches the group.)

Colonel Redips: I've picked up the vibrations of Supra-Force Metal here.

X: Colonel Redips!

Colonel Redips: What happened to the Metal?

X: Here, Colonel. Epsilon had it, but we retrieved it.

(X hands the chunk over to Redips, who appears to stare at it greedily.)

Colonel Redips: So this is it...

(Colonel Redips straightens up.)

Colonel Redips: You have performed splendidly! You are to be commended, X.

(Colonel Redips salutes X, and X responds in kind.)

X: Thank you, sir.

Colonel Redips: Now men... Return to base! A plane will arrive for you shortly.

Trivia

 * Due to Epsilon having a name based on a letter of the Greek alphabet, being a decoy final boss, and having his voice provided by Dave Petit, many fans have often compared him to Sigma, who follows the same naming convention, was voiced by Petit in Mega Man X8, and was the decoy final boss of that same game.
 * His Japanese name, Ipsilon, is actually the Greek alphabet "Υ / υ" (ypsilon) as pronounced in Modern Greek and some other languages; therefore it is possible that this Reploid was not intended to be named after the letter "Ε / ɛ" (epsilon) after all.
 * Perhaps not coincidentally, the symbol of the Rebellion looks like a capital letter ypsilon in the shape of an eagle with its wings spread.