Bad Phaedrus, bad! *hits PXY with rolled-up newspaper*
Yeah, the Light of Syberis is the most directly opposed to those trying to release Tiamat.
Seeing as she corrupts those spawned from Eberron as well, you could also stick with that though.
Maybe see if you can find something interesting in Dragons of Eberron if you have it/can get your hands on it? It has some pretty cool fluff