Complex sentence: A theory holds him as having left Ravnica entirely, indicating that he is a planeswalker and if this is so, it would make him the third oldest behind Nicol Bolas and Sorin Markov.
Split into simpler sentences: A theory holds him as having left Ravnica entirely, indicating that he is a planeswalker. If this is so, it would make him the third oldest behind Nicol Bolas and Sorin Markov.