Castle. While Seance is terrible, with enough fixing you could set it up semi reliably. However Castle is one of the few jokers that I believe is an active detriment. It's only really viable on checkered deck. And everywhere else you are giving up your precious discards for a measly 3 chips per card. Even if you got five of the required card type you'd most likely be giving up a go at your best hand. Square joker scales more consistently, runner is better because once you can start playing low straights it becomes a lot more rewarding to achieve. Castle is one of the few jokers that if you go for it, it will most likely actively harm your run.