At the location 2, you have to finish a challenge to be able to unlock the barrier. I would say the challenge is pretty tough. 4 waves. Just save your burst for the last wave

please be aware of language

please be aware of language

And the final one.?? No help.

In the third one you neglected to mention you have to fight two rune guardians at once, as well as another rune boss I forgot the name of. I am sure for some it's a given but for newer players they should be aware so they are well prepared.

I keep feeling I've wasted some of the scarlets unintentionally. I have two crystals waiting for the last stone, but it's nowhere to be found.

In starglow cavern, you have to finish the combat trial infront of the shard to lower the shield on top of the seelies.