Complex sentence: Perhaps unstable, certainly eccentric, but undeniably brilliant, it was his research that led to the creation of a Nazi vampire army out of 1,000 volunteers in the'Letztes Battalion'.
Split into simpler sentences: Perhaps unstable, certainly eccentric, but undeniably brilliant. It was his research that led to the creation of a Nazi vampire army out of 1,000 volunteers in the'Letztes Battalion'.