Bobson wrote:
You missed my point. I said that there doesn't need to be a rule preventing something unless there's a rule enabling it. That has nothing to do with whether or not something is allowed in the first place.
All the unique weapons in that section follow the same rules for magic item creation as everything else and are perfectly replicable using the rules. They are examples, if you will, of what can be achieved. An adamantine dagger is even listed in the same section after all.
I would suggest that variants on those unique weapons are quite rare...with some being simply non-existant. However I would generally rule that variants would have to be constructed by the character in question or by a skilled and trusted specialist...provided he is aware of the item in question and the magic involved.
They are unique because of the very specific combinations of magic/spells involved or due to the preferences of the craftsman who construct them. It will be up to the GM how accessaible such knowledge is to your characters though.
