From The Heroes of Might and Magic III wiki
|You enter the arena and face a pack of vicious lions. You handily defeat them, to the wild cheers of the crowd. Impressed by your skill, the aged trainer of gladiators agrees to train you in a skill of your choice.|
Arena is an Adventure Map location, that will give every visiting hero a choice to either increase attack skill +2 or defense skill +2 upon their first visit. It is not possible to leave the arena without accepting one of these bonuses.