Hi, I don't quite understand counter-spell in the Shadow and Flame quest. If it resolves I have to discard my whole hand too?

Thank you

Yeah, you'll have to discard your whole hand in addition to canceling the event itself. This is the moment in the journey through Moria where Gandalf attempts to seal a door (if I recall correctly) and the Balrog weaves a counter-spell, causing a backfire explosion (? again, going from memory) that nearly destroys Gandalf.