That's the nightwalker companion for Onamor, and his ghost form. I think you should only have 1 silver one, as you guessed. So it looks like you got an extra. They were in the white box, right?
He should also have an Efreet companion (in silver) and a ghost form for it as well, I think.
Thanks for the response guys. Yup I'm missing the silver Efreet and have dup Nightwalker.
Crap. I'll contact Ares.