How to earn Nyan Heroes?

Could you please elaborate on the process of earning Nyan Heroes? Are there specific tasks or challenges that one must complete in order to acquire these heroes? Are there any in-game rewards or bonuses for accumulating a certain number of Nyan Heroes? Additionally, is there a marketplace or trading system where players can buy and sell Nyan Heroes among themselves? Lastly, are there any potential risks or considerations that players should be aware of when it comes to earning and trading Nyan Heroes?