The Exiles first encountered the Timebroker moments after they were plucked from their own realities and gathered together. He brought them to a place outside normal time/space to explain their predicament. According to the Timebroker, they were brought together to fix imperfections in the chain of time. Each of the Exiles' home realities had been altered by ripples in time, and if they do not complete their missions, their lives would forever change for the worse.
The Timebroker claims he is truly an artificial construct - a figment cobbled together from the Exiles' collective unconscious - a way for their individual minds to cope with an unreal situation. Various members of the team have questioned his existence and have received only vague answers to any doubts they might have expressed. Giving Blink a Tallus, a bracelet device that instructs them on their missions, the Timebroker sent them on their way.
During a subsequent mission, Blink was informed that she should "beware the Timebreaker". What this means is unknown but with their doubts about the true nature of the Timebroker and his true agenda, the team is on edge. The next time the Timebroker - or Timebreaker - appears, it can be assumed the Exiles will have several serious questions for him.
His whisperings in the the ears of both sides inadvertently caused the Cataclysm. After its occurrence, he has shown little remorse or regret for his damage to the universe. Instead he now manipulates both sides, telling that they are repairing/damaging the multiverse further, and as such currently is the master of its fate, as well as giver of missions.
The Timebroker appears to be an entity able to travel through separate quantum realities and remove people from their timelines. He has stopped time in order to speak with the Exiles privately, but this could be just brief moments in time that he stretches out to accommodate their meetings. What his true power level is or where this power comes from is unknown