The Dalek Asylum housed millions of Daleks that had gone insane or malfunctioned from previous wars. The Asylum was fully automated so no supervision was required, the Dalek Parliament had no way of knowing what the battle damaged Daleks were up to.
According to legend you have a dumping ground, a planet where you lock up all the Daleks that go wrong. The battle scarred, the insane… the ones even you can’t control
The planet appeared cold and abandoned. A forcefield was put around the planet imprisoning the Daleks, the forcefield could only be controlled from inside the Asylum. The Alaska, a starliner crashed on the planet. The Daleks feared that if a ship could get through the forcefield then the Asylum Daleks may get out. The Parliament Daleks captured the Doctor, Rory and Amy and sent them to the planet to turn of the forcefield. The Parliament Dalek spaceship would then destroy the planet preventing any Daleks from escaping.
It is offensive to us to extinguish such devine hatred… does it surprise you to know the Daleks have a concept of beauty.