History - About
"the evil dimension" is not the same as you may know from episode 3.09."the wish",
where willow and xander were vampires and buffy still the slayer...
in episode 1.10. of btvs it was just a nightmare to be a vampire, which has becoming real.
but "in the evil dimension" all went wrong. buffy the vampire slayer,
fighting against all evil beings, tried to slay the master, the vampire-king of sunnydale.
but the master was stronger than buffy ever guessed.
he controlled her mind and drunk her blood. but he didn´t just killed her.
in this dimension don´t exist an vampire called "angel", only the original "angelus".
angelus didn´t love buffy, ´cause he was an evil vampire, and so he didn´t try to rescue her.
and without angel´s help xander couldn´t knew where the master and buffy were,
so buffy wasn´t rescued...
another difference you have to notice:
the master didn´t just drink buffy´s blood, no... he forced buffy to drink his blood, too,
so that buffy became a vampire... evil buffy was born.
when the master left his "prison", buffy´s friends willow (well known for her superior intellect)
and xander (who loved buffy), tried to slay the master, but both were made to vampires...
so, the scooby gang was reunited - as evil scooby gang.
willow´s wish became reality: evil willow & evil xander were a couple.
they changed their look and behaviour, ´cause they were vampires, demons.
also evil buffy found her big love - angelus, the most evil vampire she ever met.
all the things that happened in the well-known dimension
(buffy rescued a lot of people, prevented some apocalypses etc.)
didn´t happen in this evil dimension, and so...
vampires, demons and monsters rule the world.