Heres some of the ones I know.
The portal to XORIAT is in the south threnal expedition.
The portal to RISIA is in aussireux's valley.
The portal to DOLURRH is in the ruined temple of vol in the orchard.
the portal to FERNIA i'm not sure, but in a cave in the SEARING HEIGHTS would be a great spot. Those fire loving drow would find a way.
(though there were small summoning fires to fernia in the cult of the 6 temple)