The decision to have the duel out on the planet where the Demon tier was located, was a careful one. Why? There were a number of reasons, but one of the main ones was due to new information that had been received, about how closely the Dalki had been watching them lately.
They could see that the Civil war fighting was dying down and was coming to an end. If the Human's were in the Dalki's position, they wouldn't give them the chance to recover and attack them while they were recovering.
So they needed to get moving and fast. The military, Bree and Graylash family already had their main spaceship with their forces stationed and hovering just outside the planet and each ship had their own unique design as they landed.