Ok, I accidentally killed a member of The Blades, not realizing it was..

Hey, im really sorry to say, but if you got the "destiny blocked" message, you should have also read the part that said: "Either revert to an old saved game or continue playing in the doomed world you have created."

So, do that because there is no way to make amends... HOWEVER!!!! There is another way to complete the main quest!

You must be able to unlock level 100 doors though. You also must be able to kill a god-like character with over 3000 HP ^_^ Go to Vivec and go to the temple.

Unlock the door with a lock splitting scroll, spell, or enchant something to unlock lvl 100 doors. Then go inside. This is the tricky part.

You must KILL VIVEC (the god)! Save before you try this, ITS FRICKING HARD.
How I did it: I got an ebony staff enchanted to damage health 100 points on strike and a deaderic shield [from a golden saint which I summoned myself by going to the tower of Tel Brenora in Therena's chambers.

Finding the man who sells you a golden saint spell, than I used the permanent spell effect trick (Summon golden saint for 1 second + soultrap on target, aim at your feet, and cast for a permanent golden saint)] with a constant effect enchantment of heal 9 points (every second) and a ton of health potions.

Then, when vivec is dead (PHEW!) take the wraithguard(unactivated) from the corpse. It gets very tricky now (you must activate the wraithguard).

You must go to the Corprusarium (at Tel Brenora as well, i think) then save before you go inside (it sucks if you get corprus) and there is the last living dwarf in there.

He is one of the dwarves who helped make wraithguard ^_^ Now, talk to him about it, do what he tells you, he'll activate it, then make sure you save, put on the wraithguard, and now you can wield sunder and keening, the two magical blades that allow you to destroy daggoth you.

They can be found somewhere, cant remember where, than go to dagoth ur and kill him and stuff, and you win ^_^ I HAVE DONE IT BEFORE! I just dont want to waste mine and your time explaining it all!