Finally finished. I built up the interior of the Tower of Light first then went back and cleaned out then reconstructed the interior of the Tower of Darkness with Netherbrick blocks- I very much like the contrast between the dark gray basalt and the purple netherbrick. Once that was done, I decided to redo the exterior as well and replaced the torches with burning netherrack. It gives it a more fire and brimstone look and I'm pleased with the results.