Complex sentence: However, during the meeting the three are captured by the Whispermen, minions of the Great Intelligence, who uses them as bait to bring the Doctor to his tomb on the planet Trenzalore.
Split into simpler sentences: However, during the meeting the three are captured by the minions of the Great Intelligence, the Whispermen. They are then used by the Great Intelligence as a bait to bring him to his tomb on the planet Trenzalore.