Solution submitted. Thus far, this thread does not include mention of what I would consider to be Harry's greatest weapon.
He hasn't just been practicing "partial transfiguration". He's been successfully practicing discarding any notion of time, space, object or causality, in toto.
To clarify: if you do away with time, you also radically change the meaning of space. It's all just wave equations.
I can't bold that big enough.
Challenge accepted.
I've already got the seed of a solution which I'll be fleshing out and posting formally, later.
(And it took me half an hour after coming up with it, to get here, register, and figure out how to post.)
"End" can also mean "goal". This is somewhat interesting in light of EY's work at MIRI.