Complex sentence: Aresti is now a full-time member once more of Fates Warning, who released their eleventh studio album "Darkness in a Different Light" in September 2013, which was their first one with Aresti on guitar since "Inside Out" (1994).
Split into simpler sentences: Aresti is now a full-time member once more of Fates Warning and will release their eleventh studio album "Darkness in a Different Light" in September 2013. It will be their first one with Aresti on guitar since "Inside Out" (1994).