If this hypothetical largest herdstone were to be toppled I do not think it'd break the spirit of the Beastmen. If anything it would spur them on to enact bloody vengeance (which they generally are always out for anyways)

It may or may not mess with the bray shamans, depending on whether its placed where it can channel magic.

It probably wouldn’t make any difference in the grand scheme of things, just fuck with any close herds and ruin the day of nearby bray shamans

Interesting answer,thank you.

But what could then crash their spirit?

Maybe nothing for they are just mindless animals that hate civilization.

It would be like 911 multiplied by a thousand!

The Beastmen can't be broken in spirit. You'd have to wipe them all out to get rid of them.

And that is impossible too. It's said that as long as the Human Realms exist, Beastmen will always be their bane till the end of the world.

Even if the Empire, for example, would root out the forests there will still be Beastmen to fight. Beyond the reach of any mortal army really, in the Chaos Wastes and beyond.

They're fuelled by the very same thing they long for to destroy, namely civilization itself. As long as that's present in the world, Beastmen will fight on.