An army consisting of fairies and single units of centaurs was assembled (the hero Carlawn was in the save file). With the blessing of the fairy, they destroy the skeletons, which are attacking the centaurs first.
Then another question arises: where did they get 55 fairies? Especially considering that it's a Wizard's Castle. To gather so many fairies, all the heroes would need to have a squad of fairies for exchange.