@Ganymede Oops! I missed answering this... Serpent & Unicorn is, most definitely and enthusiastically, a MU* and more specifically a MUSH. And, even more specifically, a RhostMUSH 
The Amber DRPG mentioned by @Lithium was a tabletop game. But part of its rules were adopted by AmberMUSH and also influenced many of the other Amber-themed games which followed.
Hope that helps clarify things.
@Apu Yep. That's the one. Once also (briefly) known as Beyond Belgariad.
We tried to bring it back to life twice (in 2005 and 2007) but it never really picked up. Eddings just doesn't attract big crowds anymore.
It's still up, technically, but it's only ever Jarin and me on there.
@VulgarKitten - I did start creating a character on RTA (Khessen) but he's been stuck in chargen for 5 years as RL became complicated just about then 
I've been going back lately though and might yet finish setting him up... We shall see.
@icanbeyourmuse & @Ominous
Serpent & Unicorn is, indeed, based on Zelazny's books. It is set 25 years after the events of both series. Though knowledge of the books would not be required of players or coders (familiarity of the material would be a must for a GM, though).
But for those unfamiliar with the books, the basic premise is that there are two poles of reality (Amber and Chaos) with, in between them, an infinity of worlds which are only but shadows of these two realities (Earth being one such shadow). PC's tend to be from one of the two poles which gives them some powers over shadows.
Hopefully, that answers your question?
Serpent & Unicorn is an old Amber-themed MUSH that initially shut down in 2001 after a short one or two-year run.
I've decided to bring it back to life and am now officially looking for staff. Mainly coders and GM's.
The grid is already fully built and the softcode mostly written. The place was however ported from TinyMUX to RhostMUSH and so a few things have broken here and there, but nothing major.
The chargen might have to be redesigned, though. But I'm not entirely decided yet on that front, and it's certainly open for debate.
Hey everyone! I'm new to the forum and was browsing around to get a feel for the place... Saw this thread and figured it'd be a good spot to introduce myself.
Been mushing since 1996. Mostly on Amber-themed games (my first char was on AmberMUSH). Here's a list of some of the chars I've played over the years.
AmberMUSH: Andreas d'Auvalle (1996-2003) and Syvyn Sawall (2002)
ShadowStorm: Tezyryss Sawall (1999)
RivaMUSH: Denhek (1999-2007) and Sepharon (2005-2007)
GenerationsMUSH: Sylvan (2000)
Crescent City: Armand (2000)
Serpent & Unicorn: Suhuy (2000-2001) and Kavoran (2000)
Endless MUSH: Mykael (2001)
Elendor: Isendil (2007)
Chronicles of Amber: Despil (2007)
I was also staff on Serpent & Unicorn (as Nasgarath) and RivaMUSH (as Sith).
I'm currently working on relaunching S&U... and there will soon be a separate post about that
EDIT: I forgot to mention that I also hang out on a few social MU*s, sometimes as Sith (the Rhost devel mush) but mostly as Nasgarath (Gateway, M*U*S*H...)