Claim the Sky
Little is known about this godlike entity. It probably hails from the early universe, and demonstrates a real animosity toward living things and objects that it didn't create itself. With a mere thought, it can call skyscraper-sized objects into existence. In fact, over the course of billions of years, it has created entire worlds, and world-sized structures. Many of these are filled with life, though most of that life is blighted, sterile, or otherwise flawed. Despite aeons of trying, it never seems to get life exactly right.
In the last few millennia, the One finally learned some humility. Sort of. Now it seeks to learn the secret of life from already-living things, in order to improve its own creations. In the past, it has used its powers to teleport groups of creatures across interstellar distances, where it can study and test them. For example, it has twice taken groups of heroes from Earth to a planet (likely of its creation) dubbed Mystery Earth.
Motive: Impossible to ascertain
Environment: Anywhere in the universe
Health: 100
Damage Inflicted: Major wound (15 points)
Armor: 13
Movement: Long; interstellar distances between two points when calling on its celestial power of travel
Combat: The One prefers to leave combat to the various servitor creatures it has already created or newly fashions. As its action, it can create simple but powerful brutes (level 6) two or three at a time, or a single more powerful entity (level 9). These creatures may somewhat resemble the foes they fight, or may simply be protoplasmic horrors. All age and die within a few days.
Alternatively, the One can sweep away all its enemies at once by teleporting them to some distant location, such as one of its laboratory planets, which include stasis prisons (level 8) to keep newly arrived guests in line.
Finally, the One, possessed of celestial power, can attack every creature within short range with a detonation of energy composed of equal parts electricity, fire, and force. Or use that power to restore 25 health to itself or its allies, or to create skyscraper-sized structures out of thin air (which, if used in combat, it could drop on large groups of foes).
Interaction: The One can speak and understand almost any language. It generally ignores lesser beings. Getting the One's attention probably requires damaging it, at which point it may decide that the attacker is an ideal candidate for experimentation, and teleport them (and any allies) to one of its facilities.
Use: An entire apartment building in a large city has vanished. Residual celestial energy leads Silver Sentinel to the conclusion that it was kidnapped by the One.
Other Equipment: The One carries several alien devices, including a psychic crystal.
GM Intrusion (group): The One creates a kaiju to combat the PCs.