The Constant is an extradimensional entity of unknown nature and origin that influences key events to orchestrate some grand scheme.
Little to nothing is known about The Constant, as they are only seen interacting through others they have extended their reach through. Suffice to say they are an extremely advanced entity or organization with powers that near omnipotence. They exist outside of a linear perception of time, allowing them precise knowledge of the past and future.
They reach out to individuals that are at a specific point of desperation, and offers their technologically advanced aid in return for pledged loyalty. These agents are then given strict, but specific instructions to follow without question. Those that rebel are ejected from the timestream.
Though never confirmed, it is implied that they are disembodied survivors of a world that was destroyed through an interdimensional event, and seek to prevent others from suffering the same fate.
The term 'Outlier' refers to agents under The Constant's control. They move predominately work independently and unaware of each other, but have been known to be ordered into groups for more dangerous tasks.
Existing outside of the traditional dimensions, they can can perceive and to some extent manipulate the flow of time. They have the ability to repair and modify their agents in a variety of ways to better suit their needs. They also can extensively rework memories, though at some cost to their ability to function.
Though the process through which an agent to be selected is unknown, they seem to only be able to directly act upon individuals that have already been affected by some form of chronological anomaly. They can also span multiple realities and move an agent through time, as is the case with Winter.