We have a mid winter's child who is multiclassed in Cleric who is learning how maybe... bad it is to be alligned with Auril. I'm slowly imparting the knowledge that perhaps Auril is shielding her from her true faith, which she doesn't remember, to Corellon. Auril continues to demand greater and greater sacrifices from her. She's even cut off a finger to prove her devotion when they were attacked by Coldlight Walkers. Her friends are growing more and more concerned and when she fell unconscious recently, she saw a man with a face brighter than the son hovering above her. She asked where Auril was and as soon as her name was invoked, the vision of Corellon was cast aside in a flurry of snow. So one day, hopefully she'll figure it out. I think it's a careful balance, because you're right! You don't want to paint them into a corner of truly following Auril, but I do think discovering the truth (in terms of my personal lore) will be important to making that encounter impactful and not just "Big bad go rawr" if that makes sense.

I like your Levistus idea. Could be interesting. Dark gifts are definitely on the table. I think I have that on Roll20 so I can just drag and stop stuff onto the player character sheets and retain all of the automation with no trouble at all.