The Other's role is unclear, but he seems to have held the alliance between Rassilon and Omega together, and is a part of the project that produces the Hand of Omega. Omega uses the Hand on the star Qqaba (named in the comic strip Star Death by Alan Moore, DWM #47 and the novel The Infinity Doctors by Lance Parkin), and vanishes, presumed dead, in the resulting supernova which creates the Eye of Harmony.
The Other's role is unclear, but he appears to have been vital in maintaining the alliance between Rassilon and Omega, and was involved in the creation of the Hand of Omega. Omega used the Hand on the star Qqaba (as depicted in Alan Moore's comic strip "Star Death" and Lance Parkin's novel "The Infinity Doctors"), and vanished during a supernova that created the Eye of Harmony.