Come on. He was... in a trance. The Doctor said to wait! The Great Intelligence is defeated - it's links with the Earth severed.
Plan: A: the Great Intelligence; Q: What is on the verge of becoming corporeal? A: the Doctor; Q: Who challenges Padmasambhva to a mental battle? Summary: With the Great Intelligence on the verge of becoming corporeal, the Doctor challenges Padmasambhva to a mental battle in order to defeat it.