The Dalek Emperor was first introduced in the Dalek comic strip, reproduced in collective format as the Dalek Chronicles (
http://ganolan.users.btopenworld.com/Chronicles/chronicles.htm). The Emperor was originally a standard Dalek, one of those created by the blue-skinned humanoid Dalek scientist Yarvelling. After the nuclear war that devastated Skaro, it persuaded Yarvelling to build more Dalek casings for their mutated descendants. Before the last of the humanoid Daleks died, a special casing was build for the Emperor, slightly shorter than the other Daleks, with a disproportionately large spheroid head section and in gold rather than grey. This origin story is completely different from that portrayed in Genesis of the Daleks.
The Emperor first appeared on television in The Evil of the Daleks (by David Whitaker, who also wrote most of the comic strips) where it was the immobile shell described above. It should be noted that the Emperor in Evil is not Davros, the creator of the Daleks. In Remembrance of the Daleks, Davros, greatly deteriorated and physically reduced to a head in a customised Dalek casing similar to the one seen in the comic strips, was the Emperor of the Imperial Dalek faction.
http://www.answers.com/topic/dalek-variants