The Great Tower of Oldechi
The Great Tower of Oldechi is older than recorded history. No mortal creatures and few immortal creatures can recall a time before the Tower stood. It is also unknown why the Tower exists, except that the great sage Oldechi decided that it was necessary. What is known is that anybody who enters the tower loses all memory of their previous life and can never leave the tower again, but also that the tower contains incredible riches spread across thirty demiplanes, and that some fantastic reward lies at the top.