Similar to the Nu Stone, the Chanelling Stone is gained by scratching a Nu's back, namely the Nu in Frog's Forest. If you stop him and scratch his back enough, he'll hand you the Chanelling Stone.
The Chanelling Stone is very simple: the holder holds up the stone and throws it into the air. It hovers in one place. Everyone channels their energy into it, and it fires beams of appropriate energy: dark energy, ice energy, lightning energy, water energy, physical energy.