This is really firing on all cylinders, really remarkable that you were able to squeeze this out of PICO-8!
The boss design is great. The 3 bosses each felt like they were focused on different styles of combat (AOE, ranged, dueling) and yet they each also progressed some larger ideas that were woven between them (AOE attacks by Dhriti, followed by AOE attacks across little islands by Shriv). The difficulty was tuned to perfectly match the scope of the game. Each boss took me 2-3 attempts as I learnt the patterns and developed some strategies, it felt really good.
The writing was great too. There's only a handful of lines but they manage to imbue the world and the characters with a lot of substance, and the ending is very cathartic. The sparseness that is required for a PICO-8 game is turned into a strength of the storytelling.
Really really enjoyed this, thank you for making it.