Aku aku, is a Witchdoctor mask... created thousands of years ago, around the time human civilization first started to come to light. His soul is actually from the form of a human being, which was later incarnated into the wooden, magic mask which you see before you. He has always been around, trying to fight the forces of the wicked, and to aid the ones fighting for good, and whom need the aid. But he also had a brother in human form, which also did the same, forwarding his soul into a mask as well so he could live on, but his intensions were the opposite, and they fought many, many times over the millenniums and centuries...
Aku aku is (c) to Activision