While Klaus was held up inside the time-controlled Pagoda working with the nerds of Earth, Asmodeus was with the Nine Soul Bodies and Icon working to bring back Eryx and Alesi.
They needed two planet cores, so Klaus sent them away to harvest the core of the dying Mars. Then, using the Doomsday Cauldron, they were to kill another world.
The spirit of the Doomsday Cauldron was in the process of awakening, so Klaus knew killing and perhaps devouring another planet would fully awaken it.
He planned to kill two birds with one stone.
Thankfully, those he sent on the mission all had his best interests at heart, so they worked faster than they were expected to. Two days later, Mars and Pluto were out of the Earth's Solar System.
