FitzTheRuke
Legend
He could be built either way, but it would be easier to make him "feel" like a yuan-ti if you made him a yuan-ti. I don't think the Monsters of the Multiverse version of PC-race Yuan-ti even bothers to specify "pureblood" like the older version does.I am considering the Yellow Banner original character but have a question about Yassah - An NPC yuan-ti malison. He's a human body with a snake head. For racial abilities, would that count as human or Yuan-Ti? Thanks.
I'm happy to let you build whatever character you like, but it would be easier on me if you take an NPC! You are free to pick. I can imagine Yassah as a Fighter, Rogue, Ranger, or possibly even Monk (if he uses his scimitars as monk weapons). He might even be a cleric of Dendar the Night Serpent, but that seems unlikely.
He's an ally of the party, but he's not exactly their "friend" (not even the PC named Ussal, who is his equal in the local yuan-ti but is nearly an outcast.) Oh, and he definitely was sent by Ras Nsi to spy on the party, I don't mind everyone knowing (it's an open secret). His loyalty to the party can be built over time. He already respects them.
If you have an interest in Yassah (or playing a yuan-ti in general) I suggest you take him on.