The Core was the planet-wide intelligence of Raxus Prime, monitoring all activities.
In 2 BBY, the holodroid named PROXY tried to slice into the computer system but it instead took over his body. Learning everything about the galaxy outside, the Core believed that Emperor Palpatine was insufficient to bring order to chaos and that it was best suited for the job. It had PROXY lockdown the Rogue Shadow's launch codes before it could use the ship to travel the galaxy to spread its beliefs of order, organization and predictability. It used PROXY and other droids to fight Starkiller so the Core could use the Rogue Shadow. But the Dark Jedi melted the Core's computer into slag, freeing PROXY from its control.