Iron Tower of Dispater

Though several iron towers decorate the city, none are as large as the Iron Tower, Dispater - Archduke of Hell's fortress and palace. It is visible from anywhere in the city, and through enchantment magic always appears to be very close. Dispater - Archduke of Hell maintains complete control over the tower—including the capability to shift its form and interiors to match his desires—and the tower can only be entered if he permits. If Dispater - Archduke of Hell has no interest in meeting you, even reaching the tower requires tremendous effort and immense willpower.

If the characters decide to visit, they struggle to ever reach the tower. Wherever they're in the city, the tower always appears right around the next corner, but no matter how long they walk, it never gets any closer. If the characters succeed on a DC 21 Wisdom (Survival) check and spend 2d6 hours searching, they finally reach the Iron Tower. If they fail the check, they waste 2d6 hours and are no closer, but they do trigger a random encounter.

After a final push, you reach the tower. Up close it is impossibly large. You squint as you look up but cannot make out its peak. The tower feels unwelcoming, and you feel a great heat emanating from it. There is no sign of door or window—the tower simply looms over you as if in judgment.

Unless the characters have business inside of the tower (and Dispater - Archduke of Hellallows them entry) the characters can't enter.