With so many different timelines to jump between and various puzzles to solve, it's no surprise that the Radiant Historia Perfect Chronology final boss is a bit tough to beat without the help of a guide. This is because there is only one weakness that it has, and it's one that isn't explained ahead of time.
Of course, being that this is the Radiant Historia Perfect Chronology final boss, there is an obvious spoiler warning for everything ahead. If you happened to stumble upon here for some odd reason and you haven't reached this final boss, we highly recommend you turn away now. With that spoiler warning in place, let's dive right in and beat the final boss.
How to Beat the Radiant Historia Perfect Chronology Final Boss
After a crazy reveal, you are faced with fighting the villain Heiss and his Black Chronicle head-to-head. What you will notice right off the bat is that there are multiple clones of him with the real target - the Black Chronicle - in the back. Taking out the Heiss shadow clones is a relatively easy task, but you will quickly find out that the Black Chronicle is totally invulnerable.
This might cause you to repeatedly take out the Heiss shadows, only to find that the Black Chronicle will reproduce more of them forever and forever. Essentially, this is a puzzle that you must solve in order to win the Radiant Historia Perfect Chronology final boss fight.
The solution is one that is actually very simple and likens back to what you learned at the start of the game: stacking enemies on top of one another. The Black Chronicle is completely invulnerable unless you first push a Heiss shadow on top of it and attack them together. This is the only way to deal damage on it, and the only way to win against the Radiant Historia Perfect Chronology final boss.
For this, we recommend using characters that have a variety of push skills like Stocke and Gafka to easily maneuver the Heiss shadow clones on top of the Black Chronicle and win. Keep it up and you'll have it down quickly. Slight spoiler warning, but as you'll soon find out, this isn't actually the Radiant Historia Perfect Chronology final boss, but the real one is much more self-explanatory. Good luck!