So there is 1st ending when you
complete whole upper part of the mountain.
2nd ending when you
complete the gate-based enviromental puzzle
I would expect 3rd ending when you complete all obelisks, but once I've done it I haven't been able to find any trigger. Completing all 523 puzzles didn't help ether. Is there any 3rd ending? Are there any changes after completing all obelisks besides their color and fountains?