You say it was scaled up immensely, but it I remember the blog post that the False Hydra originates from correctly, it was:

- explicitly never statted
- able to grow to a point where it could challenge even high level characters
- designed primarily to provide problem-solving encounters, with combat being far from a primary focus
- taken from a blog which brewed for 5e (while the creature is certainly system-agnostic, that does reduce the number of 3.Xe DMs who would be aware of and run such a creature)