A man named Mercer discovered a new energy source in the form of a crystal he named after himself.

Mercer crystals vary in size, with more power available for longer periods from larger crystals. They range in colour from yellow to green and, once processed, have a smooth and glassy surface.

Mined under the length and breadth of the Apolli Mountains?, Mercer crystals are Elysia's? primary power source and are found in any number of technological devices, including HoPs?.

Mercer crystals are recharged by placing them in direct sunlight. How long the charge lasts depends on the strength of the sunlight and the amount of time the crystal is left to recharge, but it averages out to about six hours of power for every hour of sunlight. Even the largest crystals can only power a device for about 30 hours in standby mode.