Abyss - Troy Denning

Luke and Ben Skywalker arrive in the mysterious part of space called The Maw in search of more clues as to what caused Jacen Solo's downfall into the dark side. But they are not the only ones exploring The Maw: a Sith Master and her apprentice arrive there, too, having followed the delinquent ancient Sith ship found by Ben in The Legacy of the Force -- and they're thrilled to find Luke there, because they are determined to kill him. But there's another powerful being hiding in The Maw. It's enormously strong, purely evil, and it has its own plans for Luke Skywalker...