@Guriok.

My searching and reading have come up with the following as a potential for which monastery Guriok studied at.

Question: Which races are the NPCs Tinis Vera, Justin and Timber?

Suggestion for an existing monastery is Sech Nevali, which is located in the Mindspin Mountains, northwest of Nirmathas and west of Northern Fangwood.

I suggest reading pathwiki page (I linked for convenience) for Sech Nevali before continue to read (so everything below makes sense).

The monastery would work well for your monk learning the ways of the windstep monk.

From the pathwiki entry for Sech Nevali:

"The orders of secretive, isolationist monks correctly believe that not even orcs would brave the most treacherous mountains in the Hold of Belkzen to disturb their solitude."

"A fourth chain failed centuries ago, making the monastery sway disconcertingly in strong winds."

"In 4670 AR, Nirmathi explorers looking for a safe route to Varisia rediscovered Sech Nevali by accident. In 4673 AR, about 40 adventurous scholars from Almas University and the University of Korvosa established a hidden research station here."

"Only a dozen of these former scholars remain in the monastery, and are divided into two rival groups. Both groups have adopted the dress and name of the monastery's former occupants and worship the Peacock Spirit."

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From the pathwiki entry for storm giants living in the Kodar Mountains:

"Storm giants can also be found in the Kodar Mountains, where they are among the few creatures hardy enough to withstand the extreme climate and treacherous cliffs."

"Storm giants tend to be loners."

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Common theme being "treacherous mountains/cliffs' for why both the Kodar Mountains that storm giants like for isolation and the monks like the privacy the treacherous mountains where the monastery is.

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I googled Do monks train at the Hanging Monastery at Sech Nevali?

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While the pathwiki says that only of a dozen of the about 40 scholars who originally studied at Sech Nevali are remaining (and the dozen split into 2 sects), there could be a third group, that decided to use the Hanging Garden to train in the ways of the monk instead of studying the arcane (the leaders of the two factions are an arcanist and a wizard).

I have been working that in-game the campaign is begging in 4713 (matching up with the year the AP started being published) and the monastery was rediscovered (by accident) in 4670 (43 years (or more?) before our campaign starts, which gives potential decades that Guriok's mentor could have been training at the monastery, and is not part of one of the two existing splintered sects (who dress in the style of and worship the lawful evil Peacock Spirit deity).

So the bulk of the original scholars might be a the remnants of the original group who did not become faithful to the evil deity.

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Should you like and make that the monastery he studied at, it gives a two decent routes to make our way to Kenabres, as follows:

Travelling southeast from the mountains to the Tourondel River (that runs between Northern Fangwood and Southern Fangwood) to Lake Encarthan, travel by ship north to the Destach River, and take that river north, than across some plains to the West Sellen River, and traveling by boat/ship the rest of the way to Kenabres.

or

Travelling northwest from the mountains across the plains to the Kestrel River, taking it to Vigil, and traveling overland and by river through Ustalav, to Ardis, then traveling the rest of the way by rivers (Vhatsuntide River, Mountray River, West Sellen River).

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Would you like to go with the the Hanging Monastery being were he trained as a monk?