u/Flamecrest

So I'm putting together a Hydra deck. I definitely want [[Gargos, Vicious Watcher]] in there, obviously, which lowers my hydra costs by 4. I was also looking at [[Neverwinter Hydra]] which costs {X}{X}{G}{G}.

I was wondering how paying for the Hydra goes while Gargos is on the board. To me it would seem like this:

1. I put Neverwinter Hydra on the stack
2. I declare X=4
3. {X}{X}{G}{G} means {4}{4}{G}{G}, so {8}{G}{G}
4. Gargos pays for 4 mana, so it turns it into a 6 mana card.

However, I've been checking online (to make absolutely sure that it works like this), and I'm only getting some wonky Facebook post that doesn't answer my question completely, and the AI overview that says that if you declare X=4, then it will only cost {G}{G}.

Aside from it being an AI overview (I agree, 99/100 times it sucks), which answer is correct?