The Void Ship is a vessel originally created by the Demon of the Abyss to allow its minions to travel through the Abyss without being destroyed.
Giratina imprisoned the Demon on Krop Tor, a planet in orbit around a black hole, and the Void Ship was taken there with him. The Daleks discovered the planet and offered to free the Demon in exchange for the ship, but he refused. So instead, they forcibly took it from him then destabalized the planets orbit, plunging into the black hole.The Void Ship was given to the Cult of Skaro so they could escape the Time War. The Void Ship is one of the few things that can get out of a Time Lock, but it cannot get back in. The Cult brought the Genesis Ark with them and emerged in 2006 PLF. The Void Ship then returned to the Abyss. The Cybermen followed the Void Ship through the hole it tore in the walls of the Abyss, escaping into our universe. The Doctor allowed the ship to return to the Abyss, making a deal with the Demon that he will pull all the Daleks and Cybermen into the Abyss, leaving only the Cult of Skaro and the Cyberman Remnant alive.
When it appears in the real world it has no mass, no weight, and it emits no light, heat or sound. Because of this it gives people a strange feeling when they look at it. Either that or its beacuse there are four Daleks staring out from within it.