Quantum Power Cells are mechanical box shaped objects that harness energy from multiple alternate dimensions.
The power cells may appear to be nothing more than empty boxes, but that's only because the technology inside them exists in an unobservable quantum state that's out of phase with our dimension.
The inside of each of the boxes is lined with an unidentified rare alloy.
After reading the Darkhold, Lucy, Elias, and the other scientists on their team created several power cells which the intention of using them like batteries to power their quantum particle generator. However, after the generator was built, Elias betrayed his teammates and used each one of them as test subjects which caused them all to become trapped between dimensions, or turn into "ghosts", trapped inside the power cells.
While in prison, Elias hired the Chinatown Crew to steal one of the power cells for him, but they accidentally released Lucy when they opened the cell and she went on to free the others.