The three-eye addict specifically named the Walker. Here is the exact quote:
"
Wizard!" he trumpeted. "
Wizard! I see you! I see you, wizard! I see the things that follow, those who walk before and He Who Walks Behind! They come, they come for you!"
Here is an edited version of what Harry said after this encounter:
"...
I am marked, indelibly, with the remnants of the presence of a hunter-spirit, a sort of spectral hit man known as He Who Walks Behind...but even though the hunter-spirit had never gotten to me, the mark could still be seen upon me by those who knew how, by using the Third Sight, stretching out behind me like a long and horribly shaped shadow. Sort of a spiritual scar to remind me of the encounter.
But only a wizard had that kind of vision, ... And that junkie had been no wizard.
Was it possible that I had been wrong in my initial assessment of ThreeEye? Could the drug genuinely grant to its users the visions of the Third Sight?"
So, the three-eye addict saw the mark of HWWB. The addict also mentions "
those who walk before." Maybe that refers to other Outsiders the addict saw or it could be something Jim has retconned out of the story. I used to think it referred to the Walker we met in Cold Days, but it doesn't make sense that HWWBf or any Outsiders would be running around Chicago at that time.
Now that I think about, it might fit with my, Elaine is nemfected idea, I posted in another thread. I don't mean the three-eye addict saw Elaine, I mean he saw the Outsider magical traces that Elaine left on Harry in the moments that led up to Harry's final confrontation with Justin. It is a reach, but it fits, maybe.
Perhaps ... but what I'm suggesting is that maybe the 3-eye project was working towards not just expanding perception, but granting vanilla users enough power to perform summonings. Either through longer term use of what they were already making, or maybe Sells was stopped before he worked out a technical difficulty in getting a fully working formula.
From Nemesis' perspective, addicts who would summon some of its foot soldiers in exchange for their next hit would be pretty much ideal. It doesn't need them to be high-functioning for much else.
This is a good explanation why there were so many summoners on the barges that came to invade Demonreach in Cold Days and the summoner or summoners who; we were told in Dead Beat, called up Outsiders to fight the White Council on behalf of the Red Court. Morgan said, "
the mortal wizards who betrayed us," suggesting he believed wizards called up the Outsiders. If you don't need wizards to call up Outsiders, only a ritual and maybe someone with a minor talent, then it doesn't have to be Cowl, Peabody (in Dead Beat) or any other Black Council wizard.
The summoners on the barges were cannon fodder. No need for wizards to expose themselves to the dangers of attacking Demonreach or being in the middle of a battle between the White Coucil and Red Court.