The Maelstrom is a dark and chaotic force, that was controlled by Baron Typhonus, the person that threatened LEGO® Universe. It does so now with Sector 9. But the Maelstrom is now more powerful than ever, for it was able to create a rift preventing any minifig from exiting Sector 9. Supplies and minifigs can still get in however, so a brave band of minifigs asked for help and formed a new type of Nexus Force. However, after the Baron was finally defeated, a new ruler emerged.
Classification of this new Maelstrom ruler is still being decided by Eclipse but for now he is known as the Maelstrom Essence, the very core of the Maelstrom. The leader and the sole problem that infected Sector 9. The nature of the maelstrom appears to be that the essence of anything infected is added to the Maelstrom Essence, which controls every infected entity. Non-corrupted allies of the maelstrom have maelstrom weapons that grant a telepathic connection to the Essence. These allies get to live uninfected while doing the Maelstrom's dirty work, such as X controlling dragons.
The Maelstrom Imperium (M.I.) will consist of the maelstrom and it's allies. So far not much has been said as to what the Maelstrom Imperium will do. The nature of maelstrom is not confirmed, but evidence indicates that the maelstrom is guided by a single entity, however the essence of anything infected is added to this entity. For non-maelstrom allies, they are equipped with maelstrom weaponry (that grants telepathic contact with the essence) and follow orders, or become corrupted.