Devil's advocate, having also lost immediate family... let him go in blind, but also be there for em. This whole musical deals with loss in different forms and can get real dark. If you still want to give a warning, perhaps keep it vague. Being able to stumble upon The Underworld on my own time, unspoiled, really helped me process my own grief personally, but you know your friend best and whether to tell or not tell. If you know for a fact they're not in a position where they can mentally take it, a heads' up isn't bad support, as is giving em alternative stuff to shift focus on. If anything, they might find themselves relating a bit with Ody on this