[PeeWee]

See, I like that idea as is. The subquest sounds cool and the weapon isn't bad at all. I doubt it centers around one weapon but you could easily make it if ya wanted.

As for it having an AI or bein able to talk, and incorporating it into a story. It seems that the sword will be soulbound to the wielder. Any alignment change will affect the way the sword acts.

Remember ya said something about the paladin can turn back into lawful good. If so, you need to remember to set some triggers for the sword to revert back to it's original state. Tricky to do.

BUT, you can also have an "alter".... in order to change alignments, the lady has to hand in her sword and place it in this shelf. Out comes the new weapon. There are many ideas that can spin off from this.

The dooms and chill touch seems to be good for big baddies even when going solo against them. After 3 dooms are casted, each chill touch should deal out considerable dmg especially if the paladin is hasted; that's good melee dmg ontop of the chill touch - 2 for 1 all in one sword.