Hi.

I am returning to Sigil after quite a few years. I did not recall entering the siege tower being so difficult, until I finally search for the answer and discover that a portal is supposed to appear at the drawbridge to the right of the tower. However, nothing happens. I did defeat the abishai that was standing there. Do I need to carry anything?

Speak to the young lad Lazlo in the marketplace. If you ask him about everything, eventually he will tell you the secret of opening the portal.