A phantom knife is a magical weapon that is, presumably, very rare.[2] The blade of the knife can pass through solid matter, though the blade's tip can be made tangible at any moment and is primarily used by skilled assassins to kill without an entry wound.[1]
History
Blackwell Keep storerooms
The ridge troll Grippa who worked at Blackwell Keep mentioned that they had a single phantom knife in their storerooms and that it would be nearly impossible to replace. He was therefore unwilling to part with it when Seth Sorenson requested to borrow it.