Habolg

ハボルグ

Habolg is a well-known Black Whistle who delivered Lyza's White Whistle and final notes to the surface. Riko and the other children call him Habo-san.
Habolg was one of the delvers sent after Riko and Regu following their flight from the orphanage and solo descent into the abyss. He caught up with them quickly. For the time being, he showed respect to Regu, the Supreme Treasure of the Netherworld, because Natt and Shiggy insisted that Habolg see him. Instead of taking them back to Orth, he offered to escort them to the Seeker Camp. Understanding their situation, he then gave Riko a warning about Ozen, along with some medicine and other supplies, and let them go.
Since then, although he has not interacted directly with Riko or Regu, he has been seen on the surface telling stories to Natt and Shiggy about the abyss and its inhabitants, offering foreshadowing of the dangers that Regu and Riko will face.