Why are they blocking the mine?

Another Second Edition Warhammer game tonight.  Lord Asgard's forces are stopped before the Mines of Gwenyth-Fi by a Gnome Army.

Lord Asgard meets the Gnome Major Hero in a challenge.

The Gnome Hero falls and the whole Gnome line crumbles.

Lord Asgard accepts the Gnome Guardians of the The Mine into his army.

And on he journeys...