Bab al-Jihad — Keith A. Robinson

The only men who can save Tartarus are now prisoners. The exotic underground world of Tartarus is collapsing, and only two scientists know how to reverse the portals that will allow the population to escape back to Earth. However, before they could complete their research, they were captured by the Army of the Ahmed Caliphate and taken to the city of Bab al-Jihad. Now, their only hope lies with their friends - an unlikely mix consisting of a martial arts expert, a con man, a former soldier, a tech expert and a pair of mercenaries. The group must race against time to find a way into the heart of the city and complete their mission before the world falls apart. Yet in addition to being chased by the city's military and hunted by a team of technologically and genetically enhanced Guardians from Elysium, the group of friends will soon uncover secrets that challenge their loyalties and their core beliefs.