Workshop

However, on the night of infection, he won't die if, of course, they don't all burn. But the difficulty lies in how many heroes will burn for the player without any special abilities. As far as I remember, in the case of the Master, only one hero burned, but here the situation is slightly different.

You don't remember well. There was a fatal outcome if a pair of heroes with the required ability for burning couldn't be found. That is, 3 heroes and no special abilities – instant death after infection.
I suggest allowing players to choose any combination of heroes and abilities, but with a base cost of two, and only one being consumed during healing.