Star Trek: New Frontier Series by Peter David, John J. Ordover

Sector 221-G: For the whole of Federation history, this large area of space has been controlled by the Thallonians, a cruel, militaristic race of which little is knownexcept that they rule the other races in their sector with vicious iron hand. Now the Thallonian Empire has collapsed and the systems it once ruled are in chaos. Old hatreds are surfacing. Petty tyrants control deadly weapons. World after world is descending into disorder and self-destruction... moreSector 221-G: For the whole of Federation history, this large area of space has been controlled by the Thallonians, a cruel, militaristic race of which little is knownexcept that they rule the other races in their sector with vicious iron hand. Now the Thallonian Empire has collapsed and the systems it once ruled are in chaos. Old hatreds are surfacing. Petty tyrants control deadly weapons. World after world is descending into disorder and self-destruction. The Federation must send a starship to help where it can and report what it finds. That ship is the U.S.S. Excalibur, a newly refit Ambassador-class starship commanded by Captain Mackenzie Calhoun and manned by Starfleet's best and brightest, including some old friends from Star Trek: The Next Generation and some of the most dynamic new characters ever to crew a Federation starship. Join Captain Calhoun and the crew of the U.S.S. Excalibur as they explore strange new worlds, seek out new life and new civilizations, and boldly go where no one has gone before! less

With the fall of the ancient Thallonian Empire, civil war threatens the planet Zondar. The arrival of the USS Excalibur is greeted with relief and celebration by the anxious populace, and Captain Mackenzie Calhoun, fresh from his cataclysmic escape from the Thallonian throneworld, is acclaimed as their prophesied savior. But one believer's messiah is another's blasphemer – and a prime candidate for martyrdom... moreWith the fall of the ancient Thallonian Empire, civil war threatens the planet Zondar. The arrival of the USS Excalibur is greeted with relief and celebration by the anxious populace, and Captain Mackenzie Calhoun, fresh from his cataclysmic escape from the Thallonian throneworld, is acclaimed as their prophesied savior. But one believer's messiah is another's blasphemer – and a prime candidate for martyrdom. When Captain Calhoun is captured, Lieutenant Commander Burgoyne must find him before an alien fleet launches a holy war against the Federation! less