The Old Power is akin to the bio-spheric energy, or 'life force,' of planets. The Old Power was not formed naturally and was created by the Shadow Priests who were attempting to create an artificial version of the Power Cosmic. The Old Power is not a stable force. It has been spread throughout the universe and is said to be very abundant in the Microverse.
Old Power Abilities
The Old Power is a potent source of energy that can be tapped into by an alien race called The Shadow People. The Old Power boosts the following abilities: strength, durability, and healing--along with many other abilities if wielded properly. The Old Power grants the wielder the ability to manipulate the earth (or other planetoid) surrounding them--as well as granting them these abilities, the Old Power can turn them into a "Stone"-form. Their body is literally transformed into stone and grants them an incredible boost in strength and durability, changing someone with the equivalent strength level of Captain America (capable of bench-pressing 1200 lbs.) and augments their strength to 100 tons. In an issue of Incredible Hulks, Skaar managed to boost his strength (from about 100 tons) to 100 trillion tons - the equvialent of 200 quadrillion pounds. After someone who has used the Old Power dies, they can use the energy of the planet they died on to temporarily ressurrect themself, in a fashion that their body becomes composed of stone and they have a small electric field surrounding them. Skaar was recently killed, but came back a few panels later completely reformed from stone, so it is presumed such a process can be permanent.
Old Power's Appearance
The Old Power usually appears as a stream of electricity going around the wielder's body, and will turn the user's eyes white or blue.
Known Wielders of the Old Power
Caiera, Skaar, Hiro-Kala, Hiroim and many others of the Shadow People have wielded the Old Power; however, there has been one human who is capable of wielding the Old Power through unknown means. She is Kate Waynesboro.
It should be noted, that not every Shadow is able to use the Old power, and that it takes a tremendous amount of meditation to properly control it.
One of the feats that has been accomplished by the old power, is in Incredible Hulk #602, when Skaar uses the old power to, literally knock the Juggernaut into the atmosphere.
Yet another Old Power feat is when in Incredible Hulk #601, Skaar utilizes the Old power to destroy a Hulk-Buster armor (that Bruce Banner had created), that not even the Hulk, himself had cracked, and Skaar used the Old Power to break the top half from the lower half and send it flying a few hundred meters.