A tower in the desert. At the top waits Azazel, the mage king.

The entrance is guarded by the elite dragon guard. The teleportation circle takes them to the next floor but turns off until that floors puzzle is solved.
The second story is guarded by a stone construct. 4 pieces are missing from its body. The construct is immune to all damage until the pieces are placed into it.
The third story has a button in the fountain that starts a countdown from 20. If the timer gets to zero or is stopped at the wrong number, a magical energy burst comes out from the fountain. Numbers are found on the books, which create an equation. But the equation is out of order. To get the right number in which to stop the countdown they must put the books in the correct order. The books all have a certain number of stars on them, which help to put them in order.
The fourth floor is guarded by a statue of a minotaur. (https://www.wallydm.com/dnd-puzzles-minotaur)
The fifth floor find you in the room of the sorcerer king.