Nothing can topple you. And if it does, the fall is momentary, transient, painless, nothing but a brief pause while you find your feet again. You do not fear entering into the chasm- indeed, what is there to fear? Someone will always be there to catch you. The Black sisters, out in the snow one winter.
Christmas 1997. The Dark Lord is feeling unusually festive, Lucius is wearing a peacock on his head, Bellatrix has decorated the place with skulls and Severus is his usual long-suffering self.