|Spoiler warning: this article may contain major plot or ending details.|
Infinity Energy (Japanese: ∞エナジー Infinity Energy) is a type of energy in the Pokémon world derived from the life force of Pokémon. It was developed and harnessed by the Devon Corporation. Its development also involved research into Mega Evolution.
In the games
Pokémon X and Y
3,000 years prior to the events of Pokémon X and Y, AZ's Floette died in a war. AZ created a machine to revive his Floette, powered by the life force of many Pokémon. His rage was not settled though, so he converted the machine into the ultimate weapon and used it to end the war. This energy is what Professor Sycamore believes is what makes Mega Stones work. Specifically, when the weapon was fired, the power of the beam radiated the energy of XerneasX/YveltalY across the region and infused itself into these stones.
Pokémon Omega Ruby and Alpha Sapphire
Prior to the events of Pokémon Omega Ruby and Alpha Sapphire, Mr. Stone's grandfather, the previous president of the Devon Corporation, learned of the ultimate weapon and wished to use the same energy to help people and Pokémon. This led to Devon developing Infinity Energy. The use of this energy made Devon one of the top industries in Hoenn. Many things have since been powered using the energy, such as Submarine Explorer 1 and the rockets launched from the Mossdeep Space Center. The Devon Parts were also parts to help make the submarine run on Infinity Energy.