Key Ship

First Mentioned in the Various Terminals scattered in the halo 3 levels The Ark, The Covenant, and Halo. These ships are able to activate various portals that can allow the forerunners to reach the ark. There are at least 2 keyships implied to have existed but there is a strong thought that there are more due to one of the ships haveing been destroyed. The last ship was in possession of a character Referenced as L in the terminals. This L character was responseable for Firing the Halo Array's.

The description of a ship capeable of activateing a portal to the ark fits the Covenants converted Forerunner Dreadnaught exactly. Anything with that much energy would easily power high charity.