Eternal

Killing him is just going to complicate things for you, better to be a good little shadow and go through the proper channels in this case. You immediately go see Brother Gray and state you need to see Master Ebon.

"And why do you need to see him right now?" Brother Gray asks.
"It's about Brother Shade, I fear he's going to do something rash that could ruin everything the shadows have worked so hard for."
"What is it?"

You explain Brother Shade's plan in its entirety and how you pretended to go along with it so he wouldn't suddenly run away or attempt to attack you.

"This is a very serious accusation, but…(sigh) not really all that surprising given his behavior lately. Before we take this to Master Ebon, I'm curious to as why he approached you of all people to help him. I don't believe hearing him ever saying a good word about you, so picking you is a bit puzzling to me. Is there something you should tell me?"
"Well…I'm sort of embarrassed, but Brother Shade knew that I saw a few uh…women of low moral fiber during some of my patrols and threatened to report me, if I didn't help him."
"(Sigh) Well…I'm glad you at least had the sense to come clean in the face of a greater threat. I'll keep this from Master Ebon, but we're going to have a serious talk about your own indiscretions later! As for Brother Shade do you know where he is now?"
"I believe he's in his room getting his stuff prepared for the mission."
"Okay, I'm going to send some brothers outside his room to make sure he doesn't leave while I go fetch Master Ebon. If Brother Shade even tries to escape instead of staying put, well that's going to prove his guilt, though I'm hoping it won't come to that and he'll at least stay put and submit the proper punishment that Master Ebon deems necessary."
"What should I do?" you ask.
"You, go back to your own room and stay there until you're called for to tell your story in front of Master Ebon and Brother Shade."

You nod and head back to your bunk. Nobody is there though; they must be on their patrols. You wait a few minutes expecting Brother Gray or someone else to come get you to come confirm your story in front of Master Ebon or whoever, but nobody does. You do however begin to hear the sounds of fighting though in the halls.

"Wonderful, they can't even hold their own defectors in place." You mutter and draw your weapon. You then cast cloak on yourself and hide in one of the corners of the room with your eyes on the doorway at all times. Eventually someone enters the room, but it's not Shade, its Murk.

"Hey brother, are you in here? I just came back from patrol and heard Brother Shade is running amok through Gloom! What's going on?"
"Shhh! Quiet you idiot! He's…"

Before you can even complete that sentence, Murk is suddenly thrown face first into the floor. It would seem your instincts were right and he decided to get revenge rather than seek escape. You attempt to cast a decloak on Shade which works, but not in time for Murk to get his bearings. Shade smashes Murk's face into the floor. He may or may not have killed him, but in any event he's not going to be getting up to help you anytime soon.

"You may have prevented me from serving Dendrin like the rest of these short sighted fools, but I guarantee that you will not live to see the fruits of your treachery." He says and attacks.

You engage Shade in battle and the pair of you are fairly matched as far martial combat are concerned. The problems arise when Shade falls back on magic. He speeds himself up getting few good hits on you. You attempt to do the same thing and it helps, but you still are at a disadvantage. He matches every move you've got and has wounded you to the point where you're starting to doubt that you'll win this battle. You push yourself harder and hope your will to survive will win out. Eventually help comes in the form of several more shadows and Brother Gray.

Several bolts go flying into Shade's back and he falls to the floor in a heap. You never thought you'd think this, but you're actually glad to see the shadows this time.

"Brother are you alright?" Brother Gray asks.
"Yes, I think so (Whew) lemme catch my…ulk!" you utter and then you feel a bolt go through your heart. You look down long enough to see Shade's armbow stretched out and then the rest of his body become still for the final time.

You soon follow him, unable to believe that your service to the Empire came to such an abrupt end.
End Of Story