How to play the campaigns in the standard version of Heroes of Might and Magic V, specifically the Tribes of the East expansion.

You forget one skill/ability at a time, and immediately receive a random new one. Repeat until you have removed all the unnecessary ones: https://youtu.be/Jj-vwzZrd_4?t=66

Thank you very much.
By the way, this works without enabling cheats, and it also costs money, something like a mentor. So, whether to consider it a cheat or not is debatable.