The White Council is kind of a Joke.

[Conspiracy Theorist]

It depends on whether Nameless knew where the gate came out in Winter, remember Nameless is likely older than Mab, her and the Merlin would have been the gossip of the day, and if Nameless knew about Demonreach being built by Merlin then yes Arctis Tor is the likely destination and to be congruent Mab’s personal prison within it, so Mab is guarding the back door and behind her Mother Winter.

[Melriken]

It depends on whether Nameless knew where the gate came out in Winter, remember Nameless is likely older than Mab, her and the Merlin would have been the gossip of the day, and if Nameless knew about Demonreach being built by Merlin then yes Arctis Tor is the likely destination and to be congruent Mab’s personal prison within it, so Mab is guarding the back door and behind her Mother Winter.

No, I don't believe the island's only never never connection is Arctis Tor... Peabody knew another because I don't think he could have gotten to Arctis Tor without discovery. Gatekeeper could have taken Arctis Tor.

[Conspiracy Theorist]

Maeve brought Peabody, there is route to outside Arctis Tor to the Phobophages lair via Pell’s theatre in Chicago. Peabody uses the same way from Edinburgh to Chicago as the Senior Council, got his photo taken, hailed a cab or got a lift from Nameless to Pell’s, opened a way to the lair, met by Maeve who smuggled him into Arctis Tor and opened the way to the Island bringing a load of giant spiders from Winter.

Nameless had been expelled from Arctis Tor following Proven Guilty, it likely added to Mab’s  deduction that Maeve was hopelessly compromised the help she gave Peabody..

[Melriken]

Maeve brought Peabody, there is route to outside Arctis Tor to the Phobophages lair via Pell’s theatre in Chicago. Peabody uses the same way from Edinburgh to Chicago as the Senior Council, got his photo taken, hailed a cab or got a lift from Nameless to Pell’s, opened a way to the lair, met by Maeve who smuggled him into Arctis Tor and opened the way to the Island bringing a load of giant spiders from Winter.

Nameless had been expelled from Arctis Tor following Proven Guilty, it likely added to Mab’s  deduction that Maeve was hopelessly compromised the help she gave Peabody..

I will have to go re-read, but my understanding was that Peabody came to Chicago, poked around, left by the same Way, then came to the island with a human.  I don't think he took a Way at Pell's and I didn't think Maeve was a candidate for his companion... (I had initially assumed the pair was Cowl and Kumori so I could be getting this wrong)

[Conspiracy Theorist]

Peabody appeared on the island with one other person and the winter spiders he didn’t travel by boat, that means a Way or teleportation, the winter spiders were accosting wizards travelling the Ways, so that is the logical method. Someone high up in Winter was trying to isolate the WC from Chicago. Peabody was photographed coming out of the waypoint in Chicago, no explanation is give as to how he got from there to the Island, but we know a viable route existed from Chicago to Arctis Tor and therefore Maeve. Peabody just needed to get across town to Pell’s. It would be handy if he had an ally resident in Chicago to drop him off on Pell’s Nameless would be ideal, especially if this were his/Cowls long term plan to install Peabody as Warden.

Basically this was Cowls/Nameless  long-term plan, one of the reasons he first associated with Kemmler, and then sought Asylum in Winter. Peabody was his mole in the WC working to become Warden and access the lore of the inmates, Maeve ran interference on the Ways through Winter to Chicago and got Peabody to the Island because nemfected.