Lea is most likely Bob’s ‘father’, she is a dark muse giving inspiration in return for an early death ...
I think Lea and Mab are each likely candidates for the creation of the Bob-to-be Shadow.
Mab -- as the more-powerful, and the one prone to
r-e-a-l-l-y long-term planning -- is IMHO more likely. In this WAG, Bob is actually a deep-cover Winter agent, an invaluable tool for mortal wizards... who don't realize that Mab set Bob's original programming in place. Bob is afraid of Winter (particularly Mab) precisely because (like Lash did) he gained his independence of the programming and "went rogue." Alternatively, Bob hasn't gone rogue, and secretly is still Mab's faithful servant; he's feigning terror as part of his cover, to deflect suspicion. Every time he goes on a "scouting mission" for Harry (or any other wizard) he has a chance to touch base.
... Jim has said we have seen Bob’s parents, suggesting that we have seen a mortal from about 1200 years ago, which is the Gatekeeper
The Gatekeeper is an interesting theory! I think it among the more-likely I've seen, in fact.
Rashid + Mab ? It works rather
well, actually!
But do we know Bob's age that precisely, "about 1200 years"?
IIRC we only know that "Etienne the Enchanter" put Bob into the skull in "the Middle Ages." That might be as old as 450ish CE, as recent as 1500ish, depending on who you consult.
And I've got to point out that -- IIRC -- we know little to nothing about pre-Skull Bob... was he previously bound into a staff? A different skull? Did he lurk discorporate in caves for a century? Maybe he has a longer pre-Skull history than he has since Etienne! Maybe "Bob" was actually a "rough draft" or "proof of concept" project for what eventually became The Archive. (unlikely, I admit! But my point is: we have
very little solid info)
... possibly The prisoner in Demonreach, perhaps Nameless
Anyone imprisoned in Demonreach is frankly too-powerful for the "mortal host" role; either could have been the Supernatural Baby-Daddy.
... or here is a weird one mortal MAB before she became the Winter Lady. Timing would be right given what we know from Peace Talks, what if Mab wanted inspiration as to magic to be able to attract Merlin, got it, realised it was a death sentence and then took on the Winter Lady Mantle to survive it, as an immortal?
Merlin's orgin was -- at least,
Arthur was -- more like 1500-1600 years ago. Given the power Merlin displayed, and that we know he used time-related magic, the phrase "Merlin's Origin" may be a confounding one until canon or WoJ speaks unambiguously!
I'm not positive, but I *think* I recall WoJ that Lea elevated as Mab did; it was Mab's "patronage" that made Lea the power she is today. If I
am recalling correctly, that would preclude the Lea+
Mab combo.
But I'm pretty sure Mab's ascension was part of a much-larger event involving a Starborn, and at least Amoracchius (maybe one or both of the other Swords, too).
Bob would then certainly have the requisite knowledge of killing immortals in that instance...
I presume
most immortals have that knowledge.
Bob could have gotten it from virtually any Shadow-parent who was an immortal.