The Captain (Last Horizon #1)

"On a little-known planet, Archmage Varic Vallenar casts a grand spell to empower himself with the magical abilities of his alternate selves. The ritual works too well, granting Varic not only the magic but also the memories from six lives--including their gruesome deaths. Now Varic has power greater than any wizard in galactic history but he knows that won't be enough. The enemies he faced in those alternate lives were apocalyptic in scale. Terrors of technology and magic. Nothing that he or anyone can defeat"--