Sisters that cast Snowgrave together stay together
Seems the popular take for Dess is that she has fire powers (Don't know if it has to do with the random unused sprites of Things on Fire or just cool opposites) but I think it's more likely that the Holiday family all has ice magic, just like the Dreemurr family all has fire magic.
Also yes, this is a finished version of this sketch that I did a while back. Finally decided to finish it.