[Radek]

1. You have done well, no problems ahead. You won't need the potion at Ellysia, she is another story.
Have you killed Xydusa? If you have then it wasn't a good idea. Ellysia will not give you Snakeskin trait but the game isn't lost. You will play the game without one of your character having the trait, that's all. The correct sequence of events is:
a) Put Xydusa into sleep by means of the potion.
b) Go to Elysia, get the trait, kill her.
c) Return to Xydusa and kill it as well.

2. Role changes: change roles so that you won't lose your current capabilities. The rogue should become a ninja or a bard, the wizard and priest should become warlocks - perhaps after getting missing magic schools: therefore, the wizard will be ranger and paladin and then a warlock, the priest will be samurai and then a warlock. The warriors can become samurais or ninjas.