During the final battle of the war between the Dark Elves and the Asgardians in 2987 BC, hundreds of Arks were used in the battle. By the end of the battle, nearly all of them were destroyed during a final spiteful attack against the Asgardians by Malekith, and their remains were littered across Svartalfheim's surface, remaining there for thousands of years. Only one Ark remained, the one used by Malekith and his minions when they escaped from the battle.
The Ark was used again thousands of years later when Malekith invaded Asgard to retrieve the Aether from Jane Foster. The attack failed and the Dark Elves fled, eventually chasing Foster to Svartalfheim, where Malekith successfully took the Aether from her.
Malekith travelled to Earth, where he tried to destroy the Nine Realms using the Aether. In a battle with the Asgardian prince Thor, Malekith was defeated and both he and his Ark were teleported to Svartalfheim by Erik Selvig's teleportation devices; where Malekith was crushed under the ship's bulk.
The Arks are massive in size and scope, capable of traveling at lightspeed between worlds. They are powered by black holes, which is a common power source in Dark Elf technology. They are equipped with cloaking devices powerful enough to mask themselves even from Heimdall, although not for much time. They also act as carriers, being able to hold several Dark Elf Harrow fighters.