Complex sentence: The full, ten-step ritual that transformed Borys into a dragon caused him to go mad and embarked on a century-long defiling rampage that desolated the planet even further to feed his arcane hunger.
Split into simpler sentences: The full, ten-step ritual transformed Borys into a dragon but caused him to go mad in the process. He embarked on a century-long defiling rampage, desolating the land even further to feed his arcane hunger.