For the 1st heroic fight, it will deal 10k fixed damage. Damage cut won't be able to reduce the damage. So make sure you have over 10k health. After that, it will power up and the next burst will deal 100k fixed damage so you have to kill it before the second burst.

Also, it is best to burst during CT max as doing burst earlier will result in the boss going max CT right away. Best to bring himes that can eat orbs and use skill to increase extra orb if you are unable to kill fast enough before the next 2nd burst. At 50%, it will remove all buff and debuff so make sure to time it carefully.

Now, in the second heroic fight, you cannot increase orb, so you just have to settle for 4 orbs. Now be sure to debuff once every turn to nullify that 1 turn immunity buff or you will trigger the attack that hit very hard. At 90% and 50% health, it will gain the ability to nullify your double or triple attack, making it even harder to gain full burst. To make it worst, its burst will reduce your himes burst gauge by 50%.

At 30% health, it will perform a trigger that remove all buff and debuff and gain the unremovable debuff immunity, which you won't be able to debuff
So kill it fast as every turn below 30%, it will always deal damage to single target and remove buff except CT max.

This is quite the hardest fight so far, but persevere and you will get the well deserved Guardian of Eternity trophy.
[Event 145] Python advent reprint event-molestermoon.jpg