You can found this secret at the top of the temple with some parkour:
Where is that? And I'm looking for the third gem to open the door, but I can't find it...
It's just an easter agg of the game it's really at the top of Terran Temple by doing some parkour. and for the third gem i don't really know i just completed sunsubira entirely before going back to the temple so maybe you missed something idk
