Dragon Health Maxed Out

I went into the end with junkie gear so I could just quickly kill the dragon and be done. However, when I died the dragon’s health, which was probably at 10%, went back up to 100%! None of the crystals are left and I was really confused. So I died again on purpose after getting it to half health to test it and it did it again! It’s annoying to have to keep bringing it’s health down so please fix this.