I'm making a new character and in his/her back story I am going to come up with some checkered past that leads them to seek revenge on 2 groups of people: High Elves, Guild leaders. So this characters 2 personal main quests are going to be to kill any and all high elves which will lead to wiping out the embassy, and infiltrating and killing the leaders of the DB, Thieves Guild, Companions and the Arch Mage. A true agent of chaos, death and mayhem.

However, it occurred to me that these characters may not be capable of death as they are important to the story line. So, please spoil away. I don't want to waste my time designing and writing a back story to a second character only to find out that their mission isn't possible.

I don't think it's possible to kill any of them without some sort of mod. I play on the Playstation, though, so I wouldn't know what sort of mod you would need. You could always just pretend that after you've done your sneak attack that they're dead. I mean, it is role-playing, so it's not like you have to actually kill them as long as you can pretend you've done it.

I don't think you can kill the arch-mage. Pretty sure he's marked as essential until

(spoilers)

He dies near the end of the College questline anyway.

Almost all the guild leaders are essential. Even when they are not, it is only at a certain point. Even the bad guys are essential, I have shot that thalmor Ancano in the head every time I see his ugly face and no in the college seems to care.

Well that's no good. I hope I can buy a new PC soon and rebuy this game. Hopefully there will be a mod that allows ANY NPC to be killed and you just have to accept the consequences in quest line dead ends.

Thank you for the replies everyone.