Avengers: Infinity War - Where (And What) Are The Infinity Stones?
5. Power Stone
Where?
Contained in the Orb, which was being protected by Nova Corps on Xandar.
What?
Quite simply, it makes the user much more powerful. Channeled correctly, it increases the user's physical attributes, allows them to manipulate energy, and even has enough power to destroy an entire planet.
In Infinity War:
This is the other Infinity Stone that we know Thanos definitely collects, although there's a chance we don't actually see it happen in the movie. It's the first one he gets, as he already has it when placing the Space Stone on the Gauntlet, which means the Mad Titan destroys Nova Corps and possibly Xandar itself. The Comic-Con trailer contained footage of Thanos hurling either a planet or moon at some of the Avengers, and that's presumably thanks to the Power Stone.