4. Trenzalore
The Doctor's grave would make an apt setting for a winner takes all battle between the two. It's been revealed that a signal reverberating across space and time will draw the team of Eleven and Clara as well as more than a few enemies into the mix. Intelligence by name and indeed nature it would seem in a rather diabolical manner. The Cybermen, Daleks and Silence have been confirmed so far but it could be the case that they're pawns in the Intelligence's bigger gameplan? Using them as a sideshow before revealing its presence and the final stages of its grand scheme would be a brilliant reveal and could make for a great last stand for the man in the bow tie. Add in a possible threat to Clara's safety and that of her past/future selves at its hands in a bid to take advantage of its travel capabilities and the plot thickens rather juicily. Her mind was so close to being downloaded in 'The Bells Of Saint John' and her Victorian nanny incarnation from 'The Snowmen' was killed by another Intelligence stooge in the form of the Ice Governess- this could be another chance for the Great one to lay the hands of whichever form it takes on her once again.