The griffin is immortal.

Could you please tell me how to launch this campaign? It keeps kicking me out of the game and doesn't let me access the additional campaigns to select one.

Yesterday, the process was as follows: install Heroes of Might and Magic V - Tribes of the East, install patch 3.1 on the game, download the campaign, and place the campaign in the UserCampaigns folder of the installed game. Launch the game, create a profile, and then proceed intuitively.