Centuries ago, a colony of Ahools migrated from the volcanic caves of Indonesia to the Himalayas, drawn by ancient ley lines connecting sacred mountains worldwide. Tenzin Norgay's ancestors discovered that these rare creatures could sense disruptions in the mountain's spiritual harmony long before humans could perceive them, forging a symbiotic relationship where the Ahools warn of approaching threats while the Guardians protect their roosting caves from discovery. Their ultrasonic calls, which resonate at the same frequency as the Yeti's subsonic communications, allow them to serve as intermediaries between the human Guardians and the sacred creature they protect.

The Ahool Harbinger possesses a wingspan of over 12 feet, allowing it to soar above the highest Himalayan peaks and navigate through blinding snowstorms with uncanny precision. Its fur has evolved from black to a mottled white-blue pattern that reflects moonlight in ways that appear as natural atmospheric phenomena to untrained observers. The creature's most remarkable ability is its dual-spectrum vision that perceives both physical reality and spiritual disturbances, enabling it to detect the subtle energy signatures of those who approach the mountain with harmful intent toward the Yeti. When sensing danger, the Ahool emits a distinctive ultrasonic call that carries for miles through mountain corridors but remains inaudible to most human ears except those of the specially trained Whiteout Guardians.

The Ahool Harbinger serves as both sentinel and prophet for the Whiteout Guardians, patrolling the skies above sacred territories to detect intruders while also sensing impending spiritual disturbances that might threaten the veil between the Yeti's realm and the human world. When Dr. Banerjee's expedition begins to penetrate deeper into forbidden territory, it is the Ahool's warnings that allow Tenzin Norgay to implement protective measures, strategically manipulating weather patterns and trail markers to guide worthy seekers toward enlightenment while leading those with exploitative intentions astray.