Right, the King of Worms. Could there still be a possibility that it is the same person? Although I know he looks more Lich like in Daggerfall.
Lore-wise, Dragon Break happens in Daggerfall, which cause a split of two Mannimarcos (one get the ending of becoming a god and the other.......). So in theory, there could be two of them at the same time. I just not too happy the way they made Mannimarco a pansy generic evil in the Oblivion counterpart.
Either way, I like to think the reason for such pansiness is http://gamall-ida.com/f/files/realmannimarco_190.jpg.