User blog comment:Zathronas/Speculative author: The Grimm and the next season/@comment-78.42.186.25-20141011171528/@comment-15586611-20141012004635

Exept that, from what Dr. Oobleck said, it sounds like they grow more intellent from experience. A 1000 year old grimm would still be extremly tough, but if it hasn't actually had a chance to fight enough to realize it's instinctive tactics don't work like the Goliaths, it still wouldn't be exactly what I'd consider the biggest threat.