Macu spends his time looking for kind and giving people who he rewards in some small way. He does this by disguising himself as a needy person, maybe an injured traveler on the road, or a beggar in a town. The first person that responds kindly to him will receive some assistance in the endeavors, they will find out about the assistance when Macu has finished helping them. If a party member is simply indifferent to Macu then Macu will give the party another chance, in a different situation, if the party is still indifferent then he will leave them alone without interfering with them anymore. If the party is cruel or evil in anyway to Macu then he will punish them is some suitable way that matches their evilness. He will even show himself to them so that they will recognize him and the fact that they were evil/cruel to him.
Surnames: The Chinese were among the very first cultures to adopt the use of hereditary surnames (around 2800 BC). But the custom didn't quite catch on in Europe - at least not until the Venetian aristocracy made it popular sometime between the 10th and 11th centuries AD. What culture made it popular in your setting and why?