Obelisk

In The Pathless, returning light to obelisks across the island is a key step in lifting the curse afflicting the world. This allows the Hunter to defeat corrupted spirits that reside in each domain.

Obelisk Activation
In each plateau there are three obelisks, and each of them have a number of stones that you put in to undo the curse.

Redwood Steppe, Great Plains and Mountain tundra: 2
When you undo all three of them from their curse, a cutscene will start and all of the Obelisks will weaken the corrupted spirit that lives in that area, triggering the boss battle.

Obelisks after Kumo
After the Kumo bossfight, you will be guided towards the floating isle, and everything will look red. You can change this by going to an Obelisk and there will be a toggle you can use to change the light settings. This is useful if you want to go to more puzzles before you beat the game.