Very interesting history to this character! As I was going through the Tales of the Witch World collections, I came to a realization that there may just be two men who called themselves "Neevor" after all!
The earliest story about Neevor appears to be "Peacock Eyes". This story tells us that Neevor was a Dalesman of High Hallack who married a women from Arvon, fathered Volt of the Axe, and became a powerful mage. Their battle with an evil Mage formed (a section of) the Waste.
The next story is "Bloodspell" which has both Neevor and Ibycus as "brothers", Warders of Arvon who preside over the exile of the Were-Riders.
Next "Neevor" turns up in "The Crystal Gryphon", "Gryphon in Glory" & "Gryphon's Eyrie" and helps Kerovan & Joisan with their battles.
Next, Ibycus awakens Kethan's birthright by giving him the belt in "The Jargoon Pard".
Next, "Neevor" welcomes Aisling to Escore(!) after she is magicly transported there from Karsten.
Finally Ibycus is revealed to also go by the name of "Neevor" in "The Warding of the Witch World".
My theory is that the original Neevor appeared in both "Peacock Eyes" and "Bloodspell". It's possible he decided to travel to Arvon (when his daughter passed on, his wife drifted off and his son became Volt and left for the land that later became Estcarp) and somehow became accepted as a Warder there. Since he was of Dalesman blood, it's possible he died (of old age?) sometime after Bloodspell and gave of his powers and name to his closest friend and "brother", Ibycus of Arvon. When Ibycus traveled in High Hallack and the Waste he went by the name of "Neevor" in honor of his Dalesman friend.
Now, this is only my personal theory, but it does resolve the problems of his origin story in "Peacock Eyes" (where he is NOT called Ibycus) and the two separate individuals in "Bloodspell" rather elegantly and keeps everything canon with "The Warding of the Witch World" at the same time.
What do you guys think?