This world we live in is not the only one. Other planes exist outside of ours, other worlds. They are all connected by the Dark Tower, the hub of all existence.
Someone is attacking the beams, the spokes of the wheel of Ka. Using Breakers, psychics collected or kidnapped from across the planes and focusing them on the beams holding everything together.
In these times a call is heard. A call for the Gunslingers.

Ka is calling, will you answer?

The Gunslingers