[2021] I hit Hydra to phase 3 during its attack switch animation and it completely dissapeared.

Thanks for raising this! The team is currently working on this issue.

We have temporarily reverted changes with the Hydra in this week's game update. The Hydra Boss and regular NPCs should be working as they were before today's update.

We will continue to investigate the issues and deploy the improvements once we have resolved the issue.