The Grail – what is it?

Usually, the enemy (if the Grail is on their territory) digs it up within the first month... And that's annoying. For example, the enemy digs up a Grail near their Castle and places it. I eliminate them... And what then? What good is a Colossus, giving 2 morale, if I'm playing as Necropolis? And vice versa, it's not helpful either... :)