Okay, I had to do a little research to figure out your terminology (never heard of Eberron), but...
4. Harlyn d'Orien. Human male warmage. Dragonmarked, but relations with House Orien are a little strained. Enlisted with the Aundairian forces in the Last War, set to guarding a research facility. Released to House duties on Orien's request. Subsequently learned that the facility was destroyed, and his company missing, presumed dead. Self-described poncy character. Frequently starts encounters by either offering or seeking fine liquor.
Is back amongst his (missing, presumed dead) company. They are not dead! They are happy to see him! They are celebrating in a tavern!
Then they all start to die, horrifically. I don't know what kind of "research facility" they were guarding, but I imagine something along the lines of them all dying of Cap'n Trips from Stephen King's "The Stand". Horrible, slow, agonizing deaths as they all sit in the pub, tankards clasped in their hands. Pustules, choking on mucus, hemorrhagic fever symptoms (bleeding from eyes and mouth and similar). They are moaning and screaming, dying...and they plead with him to get the cure. He knows where it is. He can reach it easily. He stands...and is too drunk to walk. He stumbles forward but can never reach the door, he keeps going the wrong way, dizzy and confused. As the last of his mates expires, clutching at him with bloody fingers, the man (or woman, who knows?) gasps "Harlyn...it's your fault..."
And then he wakes up.
5. Seraphina Jorasco, halfling female healer. Favoured in House, not yet dragonmarked. (The player plans a Siberys mark.) Spent time in the Eldeen Reaches learning herbal rememdies from the druids there. Developed a hatred for aberrations from the Gatekeepers.
A simple thought. She has received her dragonmark. Hooray! She is proud and flushed with newfound power. Then someone points at it. She looks again.
It is wrong. It's different. It's aberrant.
Her power erupts forth (whatever that might mean) destroying all she loves. She is a monster...
And then she wakes up.
3. Ardente d'Lyrandar. Male half-elven bard. Dragonmarked, favoured in house. Works on airships, dreams of captaining one. Friends with Harlyn dÓrien.
Hindenburg. IJS.
6. Sil, changeling female rogue. Likes the 'thousand faces'lifestyle. Native of Sharn, did some freelance work for Breland during the Last War, engaged in less legal activities on her own behalf too. The player is interested in a future with either the Brelish intelligence or the Cabinet of Faces. (Or both.)
This is a good candidate for the "can't control the change" nightmare mentioned earlier. She's having a blast, wearing any face she wants. But then she can't wear any face she wants, she wears any face she sees without control. Then her features flow and shift randomly, making her a hideous monstrosity. Then her skin and muscles slough from her bones...she can feel the cool evening air on her heart, her lungs, her viscera and they begin to melt and run too...
Alternately, she's having a blast changing faces and then she can't. She can't change from the last face she wore. She can't change her *expression*. She can't move as well as she did. She is turning to stone, forever immortalized as *someone else*...
I'll give some more thought when I have a tad more time to the others.