If any of you have got the old Toa miniCD, you will know that Makuta is said to have many forms. Well, we already know about three. His Matoran form, the big tentacle-ridden thing, and his new Rahshki-esk form.
Well if you look at this picture from the new MoL trailer

You can see a pair of green eyes looming over his new form, AND if you look closely, you can make out the shape of an infected Kanohi Hau Olda.
Well. My thoery is that this huge infected Hau is the visual representation of Makuta's spirit. This is the source of all the Makuta-related evil (ie. the Rahi, Rahshki etc..) and the physical forms of Makuta are just manifestations of Makuta.
For Makuta to be defeated (which WILL be in a long long time), the Toa Nuva and any other help they get in the later storyline, will have to destroy the spirit of Makuta, using some means that we do not yet know about.
Post your thoughts on my new theory.
