How to get Yamaraja hero?

Like all other heroes you need to recruit him through the Bar using recruitment tickets. The orange scrolls will generally give you the best chance. All recruitment is random and your chances are limited but over tie you will have a good chance to get all of the standard orange heroes.

You can also try to collect fragments for any specific hero by using the Token shop to buy them. This can also take a long time depending on how actively you play.