I have an ongoing campaign, that started with a vampire-paladin who is now a blackguard — he fallen to the dark side, thanks to Nightbringer. Then he lost the sword: he wanted to control Nightbringer and so she left him. (It did not destroy him because the paladin is a fervent anti-Orcus.)
Anyway, that's just background. On to the question.
Nightbringer is a paragon-tier artifact. It is mighty, but it still is a longsword, and my player has been feeling that it does not deal enough damage. I know as the gamemaster I can change the sword to a fullblade or an execution axe... My question is, would that disrupt the balance?
Should I just not worry about it, and give my player the chance to have a better weapon and enjoy taking souls? To justify it in-game, maybe I could change it with a good "dinner" of souls?