Great Scott! Are there any images of the unknown staff-wielder from Malum’s box? 
Also, before I thought it was Metus too, but upon closer inspection it clearly doesn’t have the same skinny bent av matoran limbs…I agree with @Oonie in which it is Matoro Mahri with added-on spikes that the box artists just plopped in so that Iconox would seem more mysterious and/or alive
They’re even in the same pose!
Maybe this gives more credence to the theory that Kongu Mahri is in fact the one on Malum’s box…but I need a clearer pic to be sure