I've also dug myself deeper into sky lmao I- um.. I started playing in August and apparently I've clocked in 260 hours already.
Anyways, Elder Spirit for Isle is a lengthy beard for 6 Eden candles, I believe. That's it. I believe all you get are hairstyles so if you watch the cutscenes at the end of each level, you'll have a good idea of what you're getting. But honestly, if you're planning on completing all the spirits..
You're gonna need a lot of hearts. Like you'll eventually not even need candles, just because the amount of hearts are so hard to get in comparison. Each basic colored cape has a variant that's worth 3x the amount except for black and white. Sometimes this will bring your constellation progress to a halt, and as someone experiencing this rn.. Get some friends and start doing daily heart trades. Friend a lot of players (make sure they're active) to light their candles everyday. This will make things so much easier..