It's just that there's a certain chance to get that spell elsewhere. Books, scrolls, pandoras, stalls...
By the way, on tactics, under the Hydra's acceleration, they often make a "cabbage salad."
And I highly recommend trying to get canned goods with Hydras. When I first saw what happens there, I was surprised, then I laughed a lot.
By the way, if you're talking about playing on 200% difficulty, I'll answer that because I played a bit on that difficulty. I almost always got Wyverns on the first week on 200%. Compared to the other castles (except for Barbarians), this is a significant advantage, isn't it? This is without restarts, I should note, and without choosing a starting hero!

Орден Феникса – харизматический :) лидер