“Fedifensor” was an AD&D adventure back in Dragon #67.
The backstory is that a high priest (Astramal) of the god Amphabese, had two prophetic dreams. In the first one, his temple was overrun and by a demonic horde. The second dream was of a paladin, wielding a mighty blade, defeating a singularly powerful demon.
Distraught by these visions, he went to visit an enclave of gray elves. Convinced that his dreams were prophetic in nature, and that a horde of demons would be as bad for them as for the temple, the gray elves agreed to make a blade such as Astramal had seen in his dream.
It took years, but finally they delivered to him the blade Fedifensor. Astramal thanked them for their gift, and pledged that he would watch over the blade above his own life, and that only the most virtuous of hands would wield it.
It took months to determine who that would be, having to choose from among the paladins who came to their temple to renew their holy vows, but Astramal finally settled on Boyd de Thalion as the one to wield Fedifensor.
It seemed that no one was Boyd’s equal, until another paladin named Karl appeared. He might have also passed the tests to wield Fedifensor, save that the first test was to meet Boyd himself, upon which he immediately recognized Karl as a powerful demon in disguise. As in Astramal’s dream, they fought, and with the blade, Boyd was victorious.
Although the second dream had come to pass, Astramal’s fears about the first were not allayed in full. As such, the temple remained vigilant; rightly so. A horde of evil finally emerged from across the sea. Thousands of lesser demons succeeded where one powerful one had failed. The temple fell, and many powerful defenders, including Boyd de Thalion, died in its ultimately unsuccessful defense.
Taking the fallen champion’s blade, Astramal used a spell to send his spirit to the Astral Plane, taking Fedifensor with him. However, before he could do more, his material body was slain in a fire that had started in the temple during the battle, and the sword was lost there. A band of githyanki found it, and, determining that it was magical, took it back to their fortress on the Astral Plane, where it remains. (Until the adventurers who played this adventure recovered it, anyway.)