The One seems broken, I did both the hidden optional arena and the mandatory main quest one and didn't get it.
Same here, nothing worked.EDIT:
Upon review, I decided to bump it up to Purple status. It's clearly not functioning correctly and is seemingly broken despite numerous campaign completions.
I got A Song Unsung, so it worked for me. I don't think I got Stay Grounded, unless that means more than just handing over the heart.
I did it and followed the quest line religiously (Sebille is my fave character) and nothing.
The Seven Altars seems bugged, I visited all seven and got nothing, and it doesn't update your progress either.
Make sure you do it with one character if you're playing with someone else.
For example, my SO did 2 of them altars and I did 5; our progress showed 2/7 and 5/7 respectively. On our 2nd and 3rd play through, we made sure we each took a turn doing ALL of them by ourselves. This method earned our completion of it successfully.