Mt. Piping Hot Suckhole is used by Big Jo to kill Demons. Luci's Lawyer and an unnamed demon were thrown into the lava here. The lava likely has demon killing properties, as demons are immune to fire. There is a height limit to sacrifice, and Big Jo would have broke that rule if he had not been killing for other reasons.
The first demon thrown in the volcano could be Stacianne LeBlatt, but for the fact 'she' is missing the bow from the top of her head (which is clearly visible when she is in the cart). If it is intended to be her, then there is a continuity goof.