I would like to remind you guys that there is another game by the Oniken dev coming on February 8th. It's called Odallus: The Dark Call.
Basically, grab Oniken if you're a Ninja Gaiden fan and grab Odallus if you're a Castlevania fan. They're both really good (at least on PC), but I think Odallus is super-really-good.
I think I am more interested in Odallus but didn't they say there will be a discount if you buy both?