Sorcerer’s Citadel

Designed for a party of five characters of at least 9th level, this
adventure will challenge players seeking a powerful magic item of the
GM’s choosing. A sphere of annihilation has been provided and is woven
into several elements of the adventure, but any appropriately powerful
item can be substituted if something else suits your campaign better.
Though the adventure is designed to test every type of character class, a
rogue who can deal with traps is essential, as is a wizard or sorcerer of at
least 9th level. Larger groups will have an easier time; parties of four or
fewer characters will be in for a very bad time unless you mitigate some
of the tower’s more lethal traps and encounters. This adventure culminates
in an encounter with devils and a sphere of annihilation.
The sphere of annihilation is hidden deep within the tower-and-dungeon
complex of Crane the Sorcerer. Originally set atop a high mountain in
a secluded and wild part of the world, the tower and dungeon can be
relocated to meet the situation in your campign. Crane, an introvert,
stayed as far away from civilization as possible, as is detailed below. The
tower above the dungeon doesn’t present many difficulties for a group of
powerful characters or alert players. It might lull PCs into a false sense of
security before they enter the areas where they’ll really be put to the test.