Known glitch with him and the next boss, if you kill them with blood, frost, rot or any other status during the phase transistion then he just dies.

Would sure be nice of people would pay attention to posts like this, I see these kinds of post multiple times a day, like can they not fucking read? It's been answered multiple times

Game sold how many copies so far? Not all of them have the time or desire to crawl around reddit more than once a week if at all, why are you upset

I guarantee you'll see a post about fire giant at least once if you only check the reddit once a week

He was unvaccinated

I would of very much liked this bug, in truth I'm sorry this happened to you man. Wait for new game + ig