In my opinion, Hydras should be removed and replaced with Manticores. But their stats should be reduced: poison damage, HP, and melee damage. And Hydras should be made neutral creatures. Otherwise, a Cave Hydra with 120 HP, 30-50 HP regeneration, and "immune to gates" – I think that's cheating.
Initiative - 7
Speed - 5
You have to wait an age for it to act, but in that case, the Warlock's "Surprise Attack" ability is very effective. Cast Teleport to Enemy on the Hydras + a +50% attack bonus, and then the fun begins.
