"We can't leave yet, we have to take care of Kane and Cyrus." You say.
"What? You don't think it wouldn't be a better idea to escape and then come back with an army or something?" Edgar replies
"It would be preferable yes, but by that time they'll be entrenched and possibly already on the move with their own army of giants, ogres and orcs. That's less likely to happen without Kane or Cyrus here."
"You don't think someone else will take their place?"
"I KNOW someone else will take their place, but by getting rid of Kane and Cyrus that shaky allied army that they've built up will fall apart. It will then be far easier to handle seeing as it won't commanded by Eternals."
"Well, that's true…okay let's do it."

Edgar suggests getting some basic armor with helmets to disguise and protect yourselves in and mentions the supply room in the human section of the fort should have some. It takes some sneaking around, but Edgar's knowledge of the layout gets you there with relative ease. When you do get to the room you have to kill a couple human guards, and get dressed in some armor without raising an alarm.

At least not an obvious one.

"I told the others that you wouldn't try to escape. Glad to see I was right." A man's voice says from somewhere. You and Edgar both grab weapons and look around putting your backs to each other.
"Knew it was too easy." Edgar says.
"It still can be." The voice remarks.
"Who are you? Show yourself!" you demand.
"And have you possibly kill me? Oh no, I know the skill and ruthlessness of the Eternals all too well having served with Cyrus for years, not to mention seeing Edgar in action. And your own reputation speaks on its own, Bane of Rask. There is no need for animosity however, I am willing to help you."

"It's a Shadow Guard, he's using his blasted magic tricks to stay invisible to us." Edgar whispers.
"If you're here to help, why have you allowed this to treason to happen in the first place?" you ask still keeping your guard up.
"Oh various reasons, but let's just say the major reason is that Cyrus is a very convincing fellow. He probably doesn't seem like it to you, but he has a certain charm about him. It's how he's managed to convince Kane to go along with all this I imagine."
"So this was all Cyrus' idea." You say still scanning the room.
"Eh, it's a little more complicated than that I think, even I'm not privy to all the details. I only know as much as I do because Cyrus is a little more talkative after sex…"
"Okay, I didn't need to hear about that!" Edgar exclaims.

"Look we could stand around and talk all day until the guards realize something is wrong, or you can accept the help of me and the rest of the Shadow Guard. We have come to realize for a while now that this plan is not in our best interest and will only lead to our destruction." The voice says,
"You do realize that you have already participated in treason and this attempt at switching sides because you know you'll lose anyway, will not save you?" you say undiplomatically.
"Ha ha! Yes, I would expect no less from the Empire and especially not from an Eternal such as yourself. You Eternals, you think in such absolutes and that's why you'll be the death of us all…not YOU of course, but for the rest of us. (Sigh) I think the Shadow Guard should've broken away from the Empire years ago before you lot popped up. Anyway it hardly matters now, I'm still offering my help…"

Before the man can complete his sentence you have managed to locate his whereabouts in the room and grab him. His invisibility disappears to reveal a mundane looking man in a gray cloak. As you hold your sword to him, Edgar does likewise.

"I hate to burst your ego, but this isn't the first time an Eternal has managed to detect me, you took longer though." The gray-cloaked man says.
"How can I trust someone who has defied the Emperor and participated in treasonous acts?" you ask, ignoring the Shadow Guard's flippant nature.
"You can't. And being a Shadow Guard probably makes me even less trustworthy. The only thing I can say is you'll have to make a leap of faith Eternal. I will confess this though. The Shadow Guard's loyalty to the Empire is starting to be less than absolute. Granted there are still debates about this within our order and not everyone can decide on how we should do it. Personally I felt we should all just leave and not make a big mess about it. Obviously some, like Cyrus feel otherwise. Now I have just relayed perfectly good intelligence on a potential major threat to the Empire. You will be able to warn others after you take care of Kane and Cyrus."

You kill him

There is no way you're going to trust a Shadow Guard even if he has given you good information. He's still a traitor that would betray you at the nearest opportunity he deserves no less than death. Without another word you run him through and muffle any yelps he might've made during his death.

"Good idea, no way we could've trusted him." Edgar says.
"Come on, we should head to Kane's office, that's probably where he's at, hopefully Cyrus is there as well."

You manage to walk through the halls of the fort without difficulty thanks to the face covering helmets. Everyone just assumes you're just two soldiers going about your routines. When you arrive near the office there are several heavily armored orc guards milling around there. You and Edgar briefly wonder how quickly you can kill them before more come running, but unfortunately, when another one comes running your potential plans of distraction them are gone.

"Ay! Ay! You guyz! The prisoners have escaped! Come on!" the orc yells.
"Wha?! Well we can't leave, da boss is in his office! Go get dem shadoze ta help!" one of the guard says.
"Hey we'll tell the general and you take care of the prisoners. You orcs are tougher so you'll be able to handle the situation better than we would." You pipe up and say.
"Hmm, you might be right about us bein' stronger, but even weaklings like you should be able to handle two unarmed prisoners. We gots orders, we stay here wit da boss."

"To hell with this." Edgar suddenly says and attacks one of the orcs.

You do battle with the orcs, though it isn't an easy fight, they're obviously Kane's bodyguards for a reason. You haven't even defeated all of them yet, when Kane comes out of his office.

"What's going…assassins!" Kane shouts, not immediately realizing it's you and Edgar with your helmets on.

You attempt to engage Kane, but one of the last orc guards knocks you into the wall and attempts to get you in a bear hug. You manage to get free, and after landing a couple of good strikes, the orc collapses to one knee where upon you finish him off. You turn around in time to see Kane taking advantage of Edgar's own fight with the last orc guard. Kane runs his sword through Edgar's side. Edgar pauses his attack from the blow which allows the orc guard to follow up with a good strike with his mace.

A sickening crunch of Edgar's skull along with the clang of metal accompanies his helmet being knocked off of him. Edgar crumples to the floor and doesn't move.

"Edgar?" Kane says to himself. You waste no time more time and attack.

You dodge the last orc guard's clumsy attack with his mace while blocking Kane's own as well.

"Why are you fighting me?! We should be on the same side brother!" he exclaims desperately, realizing who you are.

The orc guard winds up another swing, and you aim low taking out his legs, when he falls to the floor, you kick Kane away from you so you can finish off the last guard.

After killing the orc, Kane attempts to attack you but fails and you land a blow across his chest and then another across his face, blinding him in one eye. He drops his weapon and staggers back holding his hand on the gaping bloody wound.

"(Pant) Why…you…I can't…" he wheezes and tries to escape past you, but you stop him completely by running him through. You wrench the sword upward to slice further into his internal organs. Blood spills out from the wound and onto the floor and your feet. He looks at you with his remaining good eye. Surprisingly, he smiles.

"I…forgive you…broth…" he gasps and dies.

You don't have time to check on Edgar or anything else when you feel several bolts go into your back. You collapse to the floor and feel that same toxin you felt when Cyrus shot you, except this time you feel a whole lot sicker, due to getting a heavier dose.

"I have to say this probably worked out a whole lot better this way. With Kane out of the way, perhaps we can use these orcs to our more direct advantage after all." You hear Cyrus remark as several Shadow Guards circle around you.

"Don't expect to wake up from this one." Is the last thing you hear before another bolt goes into your skull.