Hydras are undeniably a stellar unit when used properly, and they are one of the things the book is feared for. Just watch out for the flaming banner or fire wizards! You can help mitigate the latter somewhat by taking a Supreme Sorceress as your "HQ" (we call them Generals in fantasy
), going for Level 4 and getting that +4 to dispel bonus.
Give a man a match, and he's warm for a day.
Set a man on fire, and he's warm for the rest of his life!