The black lion has roughly the same articulation as the leg lions. His lion head contains the mechanism for the combined mode head, which gives it slightly better articulation.
However, because his mouth houses the head for the combined form of Voltron, the black lion can not roar at you, because then he just looks silly. As it is, with his mouth closed he looks like he ate a blue popsicle and stained his tongue.
He actually reminds me a lot of Razorclaw or perhaps Rampage. I do remember that as a kid, I was slightly perturbed by the fact that these would all be either female or juvenile lions due to their lack of manes. Oh, nerd children are so hard to please.
Next up, what happens when you combine all these lions together? Whatever it is, there’s no way it’s as cute as this: