Future expansions.

It seems like it could be, based on those characteristics.

Do manticores have horns and black/purple fur? As far as I know, they are usually depicted with lion or human heads, which doesn't really match with horns. However, it's quite possible to create some kind of chimera that would partially resemble manticores. Moreover, many of the characteristics of manticores (lion body, human head, and wings) were adopted by the new Necropolis creatures.

Added 1 minute later
Okay, I take back what I said; it's definitely a manticore. It also had horns in the fifth game.