Complex sentence: The castle was set to rival the size of Crac des Chevaliers but when Saladin returned, only the castle's first ring of walls was finished, standing ten metres high and only one tower was completed with the rest of the castle still unfinished.
Split into simpler sentences: The castle was set to rival the size of Crac des Chevaliers. When Saladin returned, the castle's first ring of walls was finished, standing ten metres high, but the rest of the castle was still unfinished.