Hablog

Habolg (called Habo-san by Riko and the other children) is a well-known Black Whistle, and was the person who delivered Lyza's White Whistle and final notes to the surface.

Habolg is one of the delvers sent after Riko and Reg after they had fled the orphanage and had delved into the Abyss alone. He caught up quickly, partly because he wanted to give respects to Supreme Treasure of the Netherworld, Reg, about whom he had known because Natt and Shiggy told him. Instead of taking them back to Orth, he offered to escort them to the Seeker Camp; they declined. He then gave Riko a warning about Ozen, some medicine, and other supplies, and let them go.

Since then, while he has not interacted directly with Riko or Reg, he has been shown on the surface telling stories to Natt and Shiggy about the Abyss and its inhabitants, foreshadowing the dangers that Reg and Riko will face.