The Raven and the Pig (Celwyn #2)

As the music dies, the magician Celwyn is mortally wounded. His darker, immortal brother Pelaez brings him back, barely, with his magic and the party of protagonists travel on the Nautilus to the Cape Verde Islands and the healer of immortals. During the journey, Professor Kang and Bartholomew cannot tell if Pelaez will keep his brother alive. Captain Nemo is ready to evict Pelaez forcibly, but keeping Celwyn alive is the only thing that restrains him.
After Celwyn is saved, the healer requests payment for his services. This sends the adventurers to the catacombs in Capuchin, going underground with ancient and fresh corpses, and an experience they will not forget. If it hadn't been for Captain Nemo's foresight, they would have been lost. Before it is over, several of the protagonists question why it seems everyone from warlocks and vampires to witches, seem to be congregating in their world. Through it all some of them become surprising allies, and a few of their allies turn against them.
In part II, work on the new flying machine begins in earnest bringing attention from the Mafioso and a cherub-like warlock called Duncan.