The Robe of Knowledge is located in the Summer Shop which is located in Battleon, but only around June/July.
One can find more information about AQworlds by checking the information section of their site. For outside knowledge, their wiki page also contains much invaluable information.
I don't think you can find one in aqworlds.
to find the secret 2 you have to find the ninja spy in tercessuinotlim on aqworlds.
I believe you can find the book "The Robe in any christian book store.
You can find him at the farm.
you can find it in the darkovia
i greengard
trainers
yes! (I find)
in tercessuinotlim
sewer
The Marsh