As Daniel Krispin (I need a signal...perhaps a giant Noldor?) has pointed out on numerous occasions, 666 doesn't indicate evil, but rather, imperfection. Of course, they are probably betting you not knowing that. Hell, I didn't until Daniel mentioned it.
But let's examine it from that angle. Magus is the imperfect outcome of Janus' life. The possibility in which everything that could have gone wrong, did. His mother went mad, his sister was killed, he was thrown into a hostile time period at a vulnerable age, and then, after decades of growing in power, with no regard for the lives of others he has killed or maimed, directly or indirectly, he dies during is attempt to take his revenge. Quite imperfect.
What about the 777 of Janus' life? Sadly, we have no timeline to work with in which this happens. As much as I am loathe to use such terms, it seems that Janus is fated to an existence of torment.