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shows it 100% that Tiam does get reborn also when killed (not only when giving birth).
It seems to me that Otataral is way older than its current manifestations (the otataral desert, etc). Heboric muses that otataral is created during big magical conflagrations (The Telann ritual - likely on Genabackis, the Soletaken Ritual on 7Cities, etc..) but it doesnt mean that it doesnt exist in other places since the dawn of time. It is most likley that Korabas and Tiam always existed together (as i think also did MD and FL).
Yet again it is interesting now that we know the opposition between draconic and otataral power, how come Spite uses tha latter when invoking Starvald Demelain at the release of Dejim Nebral. Maybe it's just another aspect of the "one cant exist without the other" thing. SD magic was needed to be mixed in with the other warrens to create otataral and break the wards around Dejim.
A little offtopic - whom did the OD kill on the plane of the Wastelends in DoD, around p. 250 (Kalyth gets explained the whole OD/Tiam dial by the KCCM). There is a dragon skeleton and it says that an otataral fang is driven so deep in the dragon's skull that it got torn apart from its owner's jaw. The OD is further called the Slayer and Kalyth muses it killed "your god" (=Tiam) though she is not of course sure or any reliable source.
Was it just random dragons OD was killing, is that why he was chained? The Wastelands seem to be somehow connected to dragons. All the Rooted things, and then remember that quote in RG or MT in one of the chapter headings about people heading east of Awl once, only to witness scores and scores of dragons in the sky.
Sorry for the a little bit incoherent post, but one final thought - is it possible that the OD was chained not in order to get back at him, but in order to drive Tiam away? Since she can't be killed (as we saw), maybe the way to get at her would be to chain down her counterpart. Remember that the halfbloods sealed the SD warren because the dragons "started to interfere", laying chaos and waste to all the worlds (iirc). It seems dragons and hence Tiam have always been a threat to everyone else so chaining the OD was a way to prevent that?