if i have a bit of kesai`s blood, can i open the portal to the maze right away? and where is the portal?

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>Yes, Kessai-Serris' blood is the key, so it will enable you to open the portal whenever you wish. One tip though, if you still have any outstanding quests in Sigil, complete those first, if you go through the portal it'll be a long time before you return.
As for the location of the portal, have you collected your heritage?

i don`t think i`ve collected my heritage. how to collect it?

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>Do you have the Dodecahedron (or something) from your old room at the Civic Festhall? And have you found someone who can teach you how to translate the language? Then you know the numbercode of your heritage. Go to the Advocate in the Clerk's Ward to get it, it contains a note that will enable you to get the portal.

thanks, j`aran! you`ve helped me most times in IW.
grr, this is a difficult part in Ps:T. i have to do so many things to get inside the maze.