Lots of neat ideas in here! The Seasonal damage mechanic is a fun detail, ability names evoke the dragon's theme well, and final villain action adds some nice pressure to wrap up the fight quickly.
There are some spots where abilities are referenced with what seem to be old versions of their names, and a condition is mentioned (sapped) that isn't in the game, so this could use another editing pass to clean some details up. You've also got lots of blank space to fill, would love to see some more information about the dragon and what fighting it in its domain is like.
All-in-all, you've got something fun here! Just needs some tidying up and more details. Would love to take another look at it if you make a version 2.0