The Ark is a mysterious Forerunner device from which all the Halos can be activated. At the end of Halo 2, Delta Halo is armed and then unexpectedly shut down, causing it to send a superluminal signal to all other Halos in the galaxy, putting them on standby mode. 343 Guilty Spark informs Miranda Keyes and Sergeant Johnson that the Halos must now be activated from 'The Ark'. So, where's The Ark? Rumour has it, its location is Earth, buried under the ground near New Mombasa, and the effect of the ship commanded by the Prophet of Regret jumping into slipspace inside the Earth's atmosphere, had a devastating effect on everything around it, causing the destruction of New Mombasa, and aiding in unearthing The Ark... the huge structure glimpsed in the Halo 3 trailer.
B> BLOOD GULCH
With Blood Gulch (or Coagulation as its been known since Halo 2) being one of the most fondly remembered multiplayer maps, it's highly likely we'll see its return in Halo 3. We'd much rather the older, simpler Halo 1 styling this time, though.
The Covenant will return. That's a given. What's more interesting is that we can say with some certainty that the Arbiter will be back too. He does, after all, have a substantial amount of story still left to tell. What's currently up in the air, however, is whether or not he'll be playable. Many weren't keen on the Arbiter levels in Halo 2 and felt they didn't get a big enough slice of Chief action. This time round Halo 3 will be mainly MC-led, but a piece of concept art (seen in a Halo 2 documentary) for the level shown in the announcement trailer clearly brandishes the production name for The Arbiter - 'Dervish' . This suggests old Arbi' will be playable - and maybe we can choose which side of the story we want to delve into this time.
The Drinol are Covenant bosses that didn't make it into Halo 2 - they should make an appearance in Halo 3. In the Halo 2 'Behind the Scenes' DVD, Drinol are described as huge beasts segregated from the other forces. Possessing phenomenal strength, they can smash enemy vehicles to pieces. In a recent update from Bungie themselves, with regards to what creatures they were working on, they simply said, "something big". Our bet? A Drinol Beast.
Sometime between the events of Halo and Halo 2, the Covenant discovered Earth's location. The Prophet of Regret led a small invasion force, but was surprised to find out that it was the humans' homeworld. By the end of Halo 2, the Covenant had eventually begun a full-scale invasion of Earth and, come the Halo 3 trailer, have taken over. So, will we be globetrotting in Halo 3? Probably not - but we may stray from the confines of Mombasa (See T, for more details). Africa is the most important place on Earth in regards to the Halo story - and, coincidentally, theorised to be the birthplace of humanity.
Evidence to suggest that the Forerunner and human race are one and the same manifests itself in one of the final cut-scenes of Halo: Combat Evolved. Guilty Spark, upon scanning the files of human history aboard the severely damaged Pillar of Autumn, remarks on, "Our lost time." This subtle distinction, coupled with the knowledge that Guilty Spark refers to Master Chief and Miranda Keyes as the "Reclaimer" and acts as if they have met before, could reasonably conclude that the human race is all that remains of the Forerunner. Ironic, especially when you consider how the Covenant have essentially worshipped Forerunner technology at the same time as being driven to eradicate the human race. Watch for some sort of revelation in Halo 3.