The Timebreakers are an alien race of atleast two different speices. One short and bug-like, referred to as worker caste. The other is a bit taller and resembles a cricket.
The Timebreakers somehow found their way to a mysterious crystal palace called the Panoptichron and while studying it they accidentally damaged several realities, setting off a chain-reaction. Being pacifists themselves they got the idea to gather heroes from various realities and basically force them to fix the damaged time-lines, and that is how the Exiles and Weapon X groups was born.