Hohige
Explorer
You are saying that such a monstrous race (Yuan-ti) with 9 cha will survive more than 3 seasons.You clearly don't play at an actual table. Low-charisma characters can be quite survivable. There are a couple in the party of 14th-level PCs I'm DMing for, and the party of 5 8th-level characters doesn't have anyone with a charisma higher than 13. If the PCs aren't asshats, they survive just fi--I see your problem.
He will probably die at a social encounter very quickly.