On using poison cloud units...

[HJ]

Btw, the reason you see hydras rout is that they don't die very easily due to their high HP and regeneration. Anything else that took that damage would very likely be dead long ago already, pr at least crippled by afflictions. But they do take a lot of hits due to their size, and then rout since despite their high morale they are about to fail a few checks from all those hits that land. So, 4lvl priests, and hatchlings help to keep them in place.