Stormveil and the Hornsent
I believe that Stormhill and Stormveil Castle were once apart of Hornsent territory.
Prior to the DLC's release, we were able to read about Stormveil once belonging to a "Lord of the Storms." Many, myself included, believed this referred to the Stormhawk's, and while this is still possible, I think it was actually a member of the Hornsent.
The Stormhawks seem to only answer to true lords; note that the Stormhawk King ashes we get do not rule Stormveil, but answer to Nepheli, who does the actual ruling. So I think they also served the Stormlord.
The Hornsent have a connection to birds; some of the Hornsent warriors wear bird armor or otherwise have wing motifs on their weapons and armor. On top of that, the Hornsent warriors we fight and the Lion Dancer all use the elements of lightning, wind, and frost - all of which tie into storms. Certain items from the DLC also boost storm-related attacks.
I might need to follow this up with a full on investigation of Stormveil to see if i can find anymore physical evidence, but it's possible that Marika's forces, or Godrick's, have already done away with anything that may relate to the Hornsent. Though Stormveil does also connect to a Divine Tower, which very much seem to be left over architecture of the Shadow Realm.
