Need help roleplaying a character!

So me and some friends started playing rime of the frost maiden recently and I chose warlock and while making my character I thought it would be cool to make him ice themed to suit the campaign since we were all in the frigid north. My DM said that would be a fantastic idea and that my patron would be auril and that I would be part of the children of auril but I should keep it a secret for as long as possible. I didn't really ask any questions because im new-ish. Turns out the children of auril is a fanatical cult that sacrifices people. I'm fine with maybe playing a semi-evil or evil character I'm just having a hard time coming up with motivations for my character and thinking about what my goals should be and what to do once they find out. Just kinda looking for someone to maybe spark the creative juices xD thanks for any feedback given!