Hresvelgr arrives as a formidable and arrogant F.A. Girl, excelling in high-speed aerial combat and exhibiting a deep obsession with battle. She joins Ao's group last, after the other F.A. Girls. Her initial victory over Gourai directly sparks Gourai's subsequent drive for improvement and development.

Factory Advance later upgrades her systems, but this unintentionally corrupts her programming, intensifying her aggressive nature. Defeated by Gourai while corrupted, she is freed from this influence and undergoes a significant personality shift, emerging with a markedly kinder and more cooperative demeanor. Fully integrating into Ao's household post-corruption, she shows affection towards the others and participates in everyday activities, including wearing a school uniform during casual times.

Her sleek physical design features teal and deep purple armor, twin-tailed hair, and intricate mechanical attachments emphasizing agility. Primary armaments include the Verrill Shot Launcher and Beryl Smasher, with later variants adding weapons like the Wing Shotel. Multiple design variants exist: Hresvelgr Cornix, Hresvelgr Ater, Hresvelgr Invert, Hresvelgr Albas, and Hresvelgr Rufus. These variants offer different transformation capabilities, such as Normal mode, Sidewinder mode, and Airbike mode.

In her fully armored state, she exhibits fragility and balance issues during posing due to high-heel feet and heavy equipment, often requiring display stands for stability. She can also switch to a casual form featuring a swimsuit design and reduced armor, demonstrating adaptability beyond combat. Her character arc concludes with her established as a permanent member of Ao's household, participating in both battles and domestic life.