Complex sentence: The planet chosen was Cygnus 4019: a planet that was supposed to be peaceful, however it turned out to be a "training planet" for the New Gods of Apokolips, with Desaad watching the goings on.
Split into simpler sentences: The planet chosen was Cygnus 4019: a planet that was supposed to be peaceful. However, it turned out to be a "training planet" for the New Gods of Apokolips with Desaad watching the goings on.