What's This Snake Called Again?

[SpartaDog]

So lately I've been trying to remember the name of a really awesome snake I found in an article once. But it's not working. All I remember is that it was a close relative of indigo snakes, and it had an exotic-sounding name that started with an M. Muramasa? Massasara? Something like that. And I remember something about it made it unusually badass, but I can't remember exactly what that was.

Thanks in advance!