Empatis is an energy in The Hilo book series. It gives humans the ability to love and feel. Robots are not affected by it, but it can be absorbed into the robot to make give it emotions.
The Empatis was found in Oshun by Tamir. Tamir took over all of Oshun, but when he found the Empatis he felt good in his heart and released all his prisoners. He felt love. Then he buried his sword in the ground and went to Jannus to meet Dr. Bloodmoon. He said that a power like this could rain down on us all. He gave her the Empatis and she made Razorwark with it's power. Razorwark later gave some of it to Hilo and Izzy. In All the pieces fit, Izzy gave her Empatis to Hilo, killing her. Later, Razorwark took Hilo and Izzy's Empatis and gave it all (including his Empatis) to his Robot Army.
Robots who have used Empatis before.
It looks like a green, glowing sphere of light.