After The Encampment cutsceene, with the barrel to the hydra, how many hydra kills does it actually take to get 3rd star on hydra? [What is the needed hydra kill count?]
It seams to me, as if you need a Kill count of 7. But the Encampment Hydra can't be killed, only in the Post-Game Quest A Challenge or on Bitterblack Isle. The Encampment Hydra gives a easy Barrel tossing Star however, what you already did.