Pandemonium Warden

Pandemonium Warden is a High Notorious Monster, a monster that grants special titles to players who defeat it, in Final Fantasy XI. It is initially seen in one form, but shifts when that form is defeated. It has a total of ten forms, as well as an eleventh "base form" it changes back to between shifting to the next form. Each of its eleven forms has its own HP total, and all eleven must be beaten to claim victory.

An entire party of players fighting for 18 hours were unable to defeat the monster. They were forced to retire after members of the party started to become physically ill; after such a prolonged period of gaming, they began to faint and vomit.

Following the 18 hour attempt, it was patched to only have a spawn time of two hours - if not beaten within that time, it despawns and vanishes.

It was finally defeated over half a year after it's introduction into Final Fantasy XI, with only minutes left on the clock.