Hjornskar seems like a loyal warrior, and obviously a "true nord" in the eyes of Ulfric Stormcloak. Hjornskar was promoted to the rank of officer sometime before the Battle for Whiterun.
Hjornskar can be found in Dragonsreach in Whiterun after completing the quest "Battle for Whiterun" for the Stormcloaks. He is also an essential character, so he cannot be killed by the Dragonborn if sided with the Imperials during the Civil War.
- "Stormblade, it's an honor." —If the Dragonborn has completed "The Battle for Fort Snowhawk"