Originally Posted by
Nitros14
It means limited attempts of some kind.
Nefarian took 15 minutes to respawn after a wipe.
Ragnaros was only up for one hour per week.
Algalon was only up for one hour per week.
The Lich King only allowed 20? attempts per week shared amongst all end bosses (eventually 50 it increased every week.) I don't remember precisely what the count was at when it first came out.
Ra-Den only allowed 30 attempts per week.
Anub'arak only allowed 50 attempts per week shared amongst all bosses.
Lady Vashj also has an asterisk because she was killed, sort of, due to the encounter bugging out which Nihilum claimed as a world first but the first kill without bugs was later.