Later, when Sebastian Malvern, to whom Tko-Ma had connected, suspected the Cylox' true intentions, he had the Magnate's ESPnets drain the energy from Tko-Ma's dimension. The Sixth Doctor convinced him to entrap himself in a fragment of the dimension to save himself. The Doctor then gave the fragment to the Ini-Ma so she could trap the brother as well.
However, what the Doctor did not know was the Ini-Ma was actually the jailer for the Cylox brothers. Rather than risk them trying to escape again, she unleashed energy to destroy herself and them, which killed van Cheaden as well. (PROSE: Instruments of Darkness)