Legion and Legion Core? Don't worry your not missing much.
It's not a bad game really. To me it was a huge step up from Lament of Innocence which was also pretty good, but had slight minor flaws that sort of made it hard to play with (No freedom over the camera and you couldn't use Items while in the main menu and only by the quick menu). I wouldn't mind seeing another 3D Castlevania. Lots of room to improve and whatnot.