I have to say i really don t understand what this arcane portal is.
I got a code for it with the KS but where do i use it?
I guess its not the same book i received with wave 2 isn't it?
Arcane Portal is the next chapter after you finish the core campaign. It is considered to be a line of sidequests of act 1. You got all the tiles and minis (e.g. the efreets & the cultists) for Arcane Portal with wave 1 and all the needed cards with wave 2. Unlike retail customers, we KS backers didn't get a printed version of the storybook and book of secrets. Instead, you will have to download some not-that-hi-res PDFs from the Sword & Sorcery homepage and print them yourself (or read them on your tablet or whatever floats your boat).
Edit: I have no idea which code you are talking about. The only codes I got, are for unlocking characters in the app and another code for that what they deem to call a "soundtrack" via the Battlebards homepage.