"flying three flags depicting an eye, a pegasus, and a hydra"
I don't have the army book, but there are a few Total War: Warhammer Dark Elf factions that have banners that match those.
The eye might be the
Drackla Coven. The pegasus is almost certainly the
Cult of Pleasure, Morathi's faction, and the hydra could be
Clar Karond.
The first two seem to definitely be magic related, and it's not like it would be impossible for a sorceror to come from Clar Karond. Or it could just be a matter of ship procurement.