Thank you for the answers!
And what is the minimum native army for the Swamp faction to be able to capture the maximum-level Conservatory (5 stacks of 40 Griffins) so that the exchange is equal (if possible, with a description of the battle turn by turn)?
I lied, you need 3 of them. The Gnolls and 1 or 2 Hydras die. I don't know what it depends on.