He then incapacitated the others and declared he was a servant of Molag Bal, and the ritual was actually one that would weaken the barriers between Mundus and Coldharbour. The ritual turned out to be an elaborate trick by Mannimarco. Mannimarco and Varen were part of a group referred to as the Five Companions, which also included Sai Sahan, Lyris Titanborn and Abnur Tharn. Varen desired to further legitimize his claim to the Imperial throne by lighting the Dragonfires in the Temple of the One in the Imperial City, which can only be done by one of the Dragon Blood. In 2E 578, Emperor Varen Aquilarios was convinced by Mannimarco that he knew a ritual which would allow him to become Dragonborn.
And as enemies rise faster than allies, salvation cannot come from one hero alone, but from many.' ―Intro of The Elder Scrolls: Online