Great read Vernoona, thanks! I could happily live without having ever heard of the Cythrons, Leysers or El-Worlds, but it's not entirely fair to say that all the SF elements dumped on us in Time Killer were unprecedented - as I never seem to tire of harping on about, time-travel and its connection to the Drunes is right there on the very first page of Slaine, and it's also far from alien from Celtic myth. The Ever-living Ones of Dinas Emrys are referenced several times in the early part of the strip, the technological harnessing of Earth-power and Atlantis gets a nod too.
Mills definitely takes us away very abruptly from what we've learnt to love about the series, the dream-time wanderings of a properly European Conan drawn with a deep sense of landscape and cultural context by Bellardinelli and McMahon, and places us in the larger vaguely Moorcockian world that surrounds and supports it. I hated it all passionately at the time, right up to Slaine's Professor Hulk moment in the arena, when it starts to get interesting - but I've come round to the idea that this cross-time antediluvian techno-fantasy is as much a part of modern myths of the imagined past as anything else in the strip, and was in any event always hidden in the background. The shift in Slaine's consciousness (however temporary!), and ours, was an essential stage in his story.
Keep up the reviews, they're great.