The Heart of Alchemy - The Portal Wars Saga, #6

With the Chamber of Eternity secure, Otto must now recover the second piece of the Immortality Engine. But that task will be far from easy. For the second piece, The Heart of Alchemy, lies far to the east in the fabled Celestial Empire. Assassins, undead, monstrous beast, and demon worshippers all stand between Otto and his prize. And even more daunting, Valtan, the last living arcane lord, is determined to stop him.
The cost be damned. Can Otto overcome the forces arrayed against him and take the next step down the road to immortality? Find out in The Heart of Alchemy, the sixth book in the Portal Wars Saga.