I just got 15 skeins of this yarn and I have no clue what to do

Maybe a sweater? :>
Here is a topic that has a ton of awesome sweater patterns in the comments!
15 is quite a bit! I would recommend an Afghan.. If you have some extra pink and green I’ve been dying to make this one!
https://www.etsy.com/listing/1649260068/vintage-afghan-crochet-pattern-romantic?epik=dj0yJnU9YU1pQTdWLUpiWE5ScGZ2cmwxTXRYWjRFTTh2UGkzRjcmcD0wJm49ekVNTzZmX1ZPTjhKLXhqZ0R4dGJfQSZ0PUFBQUFBR2l2VG5R
Maybe a messenger bag or granny squares?
Make a detailed granny blanket. And with the leftovers make a snake or chicken
You could make some market bags a blanket would be the best way to use up yarn tho