The analyses of a convoluted text

The protagonist, one of the Amber's princes, and one of his brothers are going to the Grove of the Unicorn.
Kovlvir is the mountain the palace of Amber is sitting on.

The Grove of the Unicorn lies in Arden to the south of Kolvir, near to that jutting place where the land begins its final descent into the valley called Garnath.
...................................
It was to this place that Gerad and I rode the following day, leaving at an hour that found us halfway down our trail from Kolvir before the sun skipped flakes of light across the ocean, then cast its whole bucketful against the sky.
Gerad drew rein as it was doing this. He dismounted then and motioned to me to do the same.
["Sign of The Unicorn" of The Great Book of Amber by Roger Zelazny]
I'd like to know if the subject of the participle is "leaving."
And I'd like to know if the subject of "found" is "hour."
And I'd like to know if the starting point of them is the mountainside of Kovlvir.
Thank you in advance for your help.