The Time Cube by Adair Hart

Evaran and the gang travel to a galaxy in the Horologium-Reticulum Supercluster in AD 801,699 to deal with not one summons, as they usually do, but two that are related to each other. The retrieval of Dalton Kingston is one summons, and the second is a day ahead to a ship a few light years away.

The problem is that the summonses lead the gang into the Tenagrin Hegemony, a brutal empire run by the Tenagrins, a snake-like species who have advanced far beyond their natural technological evolution. Another issue is they also want to retrieve Dalton Kingston and have a vested interest in the second summons.

Kess, from a previous adventure, joins up for this outing, and with some new allies, they will need to deal with not only the summonses but the Tenagrin Hegemony and a galactic region that fears humanoids.