R-27SG is Calidus Shadow Ghost and is a recolored version of the normal R-27. This was an convention exclusive and extremely limited.
Calidus's energy bow can be mounted to his backpack in robot mode, and it forms the car's fender in racing car mode. First drop of Calidus will include a bonus head which will be revealed before the official release. Calidus has a very good articulation system including wrist ball joints and pull-out shoulder joints which will enable him to achieve expressive poses.