It takes a while to gather 10,000 skeletons... I managed to get a maximum of 5,000, but my opponent already had 25 Black Dragons:).
And those griffins were neutral – therefore, without artifacts. Griffins have this feature: they fly up, and you wait, wondering where this beast will land. There were no other creatures in that battle besides the griffins. Imagine the scene: an army of one color stands on the right, and there's nothing else:)! And what do you do?
Wait and be afraid... :) ... and as soon as they land, attack them immediately :)
But usually, the computer doesn't fly them up... it's stupid...