To find the next passage follow the path and climb up a ledge from where you fist see the next portal. Go around the spire to the right then head straight towards the portal until you find a place of power:
Turn right and go down the path. Be careful when you drop down both the cliff at the end, stick close to the wall to the right to minimize fall damage. Go back up the the platform ahead. Then go back down the other side and quickly run through the fog to the ledge ahead:
Now go straight towards the portal by following the quest marker.