You don't even need scarabs to win, either. Mummies are capable of doing it themselves. It's just an added boost/bonus when you get to them.
If you go first, it's possible to have 4 scarabs on the first turn, or 8 by the second turn, depending on draws (although, of course highly unlikely). If you go second, it's possible to have 6 scarabs on the first turn or 9 on the 2nd. It's not very unlikely to have 2 out by turn 3 or 4 though. All you need for that is a Mummy, Nova, RT, and SoR, each of which I have 4 or more of.
@ mesaprotector: The idea behidn this back is that it doesn't need
other than what you get from Novas due to SoR's. You could also argue that
isn't needed in your deck for the same reason, but I've learned to rely on Momentum...and your deck is very limited on devouring (even with SoR's used on scarabs).