Star Wars: Dawn of the Jedi, Volume 3: Force War

The alien Rakata--powerful users of the dark side of the Force--invade the Tython system to enslave the Je'daii! With Forcesabers in hand, the Je'daii, teamed with mad Daegen Lok and the mysterious Force Hound Xesh, meet the Rakata and their fierce Flesh Raiders in battle. But an attack on the Rakatan stronghold leads to Xesh's capture, the revelation of a spy, and new knowledge about a mysterious device on the Je'daii's own homeworld. When the direction of the war is changed, all hope depends on the love between two young Je'daii! 
"Ostrander and Duursema have reverse-engineered the setting, characters, and Force philosophies to create a fully believable 'real' ancient history of the Jedi." -Fan Girl Blog