Before Puzzlebox, there have been previous universes -- attempts at wonderful sentience and [endless creation] that, for whatever tragic reason, did not completely survive, except perhaps in the memories of those transuniversal beings (like the Transcendi) that lived through those experiences.
One such universe was Aleph.
Aleph had the dubious distinction of being Mel's second glorious failure (Mel's first glorious failure is something only he knows about and he is recalcitrant to discuss that one so far; apparently 16 reminds him of his creator). For reasons that are known only to him and Sebkha, and which are only vaguely remembered by Caroline, Aleph did not persevere despite the Museum's best efforts, the myriad pocket universes and exhibits connected to it lost to entropy. Only the faint traces of these places are left in the halls and nexi, doors and portals that suggest what might have been there at one time, closed forever.
More information can be found about the incident and "Hydra/Alpha" can be found under Mel's past-self, Benjamin.
(The important aspects of Mel were solidified around the mid 90's on Aleph, a MUCK which his player managed. The Museum housed a good dozen worlds ranging from full settings to room-based 'concept and performance art'. The MUCK folded in 1997; of the database, only the Museum halls survived, the exhibits being lost in 1998. The events of his past online experiences are valid to his presence on Puzzlebox, including the tragic loss of the original incarnation of the Museum.)
"Aleph? Destroyed? By Me? Of course not. I am only old, not ancient. Hush now, there is bleeding to be done." -Inhatti