The story behind mine is that I used to like Tool, and when Lateralus came out, I was looking at the tracklist, and one was called Mantra and the one after was called Schism. I said them together. I thought it sounded cool. A new screenname was born.
After that, my nick became significant in other ways. I went through a time of bad 'spiritual' uncertainty. I figured a 'mantra' was like a religious chant, in a way, and a 'schism' is a severe fracture in a faith, e.g. Catholicism and Protestantism being two very different takes on Christianity. I felt like I was telling myself that I believed one thing, but I didn't really, so it was like a split between what I wanted to believe and what I did believe. Which was really nothing. This is probably pretty inaccurate, actually -- I remember that there was something more to it, or something different, but that was a while ago and I don't remember anymore. I kind of wish I could. Now I feel like Mantraschism doesn't really fit anymore.
My first nick was Fates Guardian, which I still use. This one is really simple: Fates Warning + Blind Guardian (my favorite band) = Fates Guardian. Again, I thought it sounded cool, and it worked well for online gaming, and it has just stuck. Actually, I guess my REAL first one was Krakatau, from an Yngwie song, which is the name of a volcano. I've also used Sméagol, too -- pretty obvious. Sometimes I use Grymskald, or just Skáld, the former being Swedish or Norwegian for 'grim-skald' or 'grim-poet/musician', since I play music and write lyrics which are dark. Skáld is just Icelandic for, well, 'skald'. I think it's a cool word, and Icelandic owns. \m/
Now you have my biography.