User blog comment:B214/Volume 17 spoilers./@comment-16281343-20140220064813

Just some miscellaneous info..

Malebolge on Saji's BB's name, "Malebolge Vritra Promotion" is the eighth circle of hell in Dante's Inferno. You can search for that for added information.

The thing is if someone tries to escape from there, there are monsters armed with grappling hooks to prevent them from escaping. That maybe the reason why in Saji's BB's illustration, he has things that look like grappling hooks with him.