A sliver of ice is enough to kill if taken and stabbed in the right place.
He pauses on the narrow ledge, before slowly and deliberately lowering his body off the sheer ice cliff face. The inexplicable actions of a madman, whose grip on reality is slipping as fast as on the handle of his umbrella - all that now keeps him in this world. But I see what nobody else sees, what even the Doctor himself can only begin to suspect. For while he has lived many lives, I have lived countless more. And I have spent all of them fighting the one war that the Doctor cannot win. His Great Unending War that he's losing without even know he is in. His triumphs rewritten as failure by an Intelligence not above taking pleasure in petty tricks of the mind. I was there on Galifrey when the Doctor stole his Tardis. Over all the years since, he has never been predictable - except in one regard, why does he ever place himself in danger? Easy enough to plant the illusion of one more cry for help, one more life to be saved.
"It's no use Doctor. I've located the Ice Garden but there's a distinct absence of dragon or treasure." The mercenary Sabalom Glitz peered down from above the ledge.
"I sympathise with your disappointment but I'm about to plummet to my death."
"Well, what in the name of Salostophus are you doing down there? I suppose you'd like me to risk my neck saving you." Sabalom reached down, grabbing hold of the Doctor's wrist and unceremoniously pulling him to safety "That's another one you owe me. And not just me, if it hadn't been for that girl..."
"What girl?, Ace?"
"No, not her. Not that annoying loud one either before you ask. Back in the Ice Garden. She said you were in trouble. I don't know about you Doctor, but I make it a rule in life to listen to pretty girls. If they say stay, you should stay. If they tell you to run, then you'd better start running."