What exactly is/was the Beat Mesa, and what role did it play in Sburb and The Scratch?

The Beat Mesa is a construct that holds a massive amount of temporal energy that Skaia needs in order to enact the Scratch.

Basically, it’s like a fire hydrant that you crack open when there are too many irons in the fire. And the hose directs the water to make the fire go out so things can go smoothly next time.