I assume Russ will stop me if I mess up, spill too much, or contradict alterations being made for the 4e version, but since this stuff has already been 'spoiled' per se in the 3.5 release, here goes.
And, um, players, don't read. Hush Hush GM Stuff.
[sblock]60+ years ago (I can't recall the timeline), then warlord Coaltongue took Syana's daughter Trilla hostage to try to extract power from the kid, and keep the mom at bay. That didn't turn out well, Trilla got infused with bad magical energy, and she started creating semi-alive things whenever she had a strong dream. A demon/devil thigh bone Coaltongue had to use as an impromptu club managed to capture a sliver of Trilla's soul, and combined with some other magic it turned into the Torch of the Burning Sky.
Coaltongue got away, and would eventually realize the immense tactical advantage the Torch gave him. Later -- I don't recall the precise chronology, but some time before 40 years ago -- Coaltongue goes up against Syana again, and this time he defeats her. He puts her skeleton up as a trophy in his new castle in Sindaire (which will show up in Adventure 6).
After this, elvish ruler Shaaladel tried to capture Trilla to recreate the accident that made the Torch, so he could have a 'Torch' for himself. Shaaladel had allied with the half-orc warlord, but he always saw himself as the rightful leader. The effort to recreate the Torch did not turn out well, and ties into the events of adventure 7.
Somewhere around here, after kidnapping one, escape one, mother's death, and then kidnapping two, Trilla has a dream that manifests as Indomitability. The newly alive spirit wanders, unaware of what it is. Eventually it finds its way to Innenotdar.
People friendly to Trilla rescue her, and to keep her away from those who would harm her, they guide her into the underdark, through tunnels near/beneath Gate Pass (tied into adventure 9). The poor kid dragon has been traumatized a lot, so her nightmares have been getting stronger (one of which shows up in adventure 8), and eventually, after she starts a lair in the Underdark, her children the trillith take over and imprison her. (Indomitability is thus of the same family as the other trillith, but he didn't grow up with them.) This is pretty key to the events of adventure 10.
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Any other questions? And again, if the folks working on the 4e version would like me to leave it to y'all to handle the answers, just let me know. I'm just trying to help.