There are 4 books in the Witches of Karres series. The newest book is The Shaman of Karres which came out in 2020.

2
The Wizard of Karres

By Mercedes Lackey , Eric Flint , Dave Freer

Book cover of The Wizard of Karres
It just wasn't fair! Captain Pausert had foiled the deadliest of space pirates and eliminated the threat of the Worm World, yet his troubles just kept piling up. The Empress Haile herself sent him on a secret mission to stop the nanite plague, a self-aware disease that could devastate whole…

4
The Shaman of Karres

By Eric Flint , Dave Freer,

Book cover of The Shaman of Karres
Captain Pausert just can't catch a break!

First, he became the mortal enemy of his fiancee, his home planet, the Empire-and even the Worm World, the darkest threat to mankind in all of space. All because he helped rescue three slave children from their m