Complex sentence: As the Doctor is unconscious and it seems that the entity is trying to enter the TARDIS, the Cloister Bell starts to ring and Clara uses the telepathic circuit to trigger the TARDIS' depature.
Split into simpler sentences: As the Doctor is unconscious and it seems that the entity is trying to enter the TARDIS. The Cloister Bell starts to ring and Clara uses the telepathic circuit to trigger the TARDIS' depature.