Heather and Davis Cameron were a lifeguard and a surfer, respectively, living in Surfer's Paradise in Australia. Unbeknownst to them, their father was an underworld crime lord known as Viceroy, and upon his death, they were attacked.
Together with Storm and Thunderbird, they managed to defeat their attackers. Heather discovered she was a mutant with the power to manifest whatever was necessary to save the life of someone in danger around her, including her own. Heather soon joined the splinter team of X-Men, and formed a romance with Thunderbird.
During a mission to infiltrate the ship of the intergalactic warlord, Khan, Heather's appearance changed to resemble the alien Shi'ar race, and it was theorized that she and Davis had some Shi'ar heritage. Her brother, unable to see past her new, alien appearance, left the team, and both Lifeguard and Thunderbird went in search of him.
Lifeguard and Thunderbird turned up in Mumbai, India, helping out with the local X-Corporation, until the catastrophic events of M-Day and attacks on X-Corporation offices in Paris led Cyclops to call for the disbanding of all branches.
Heather was one of a handful of mutants to have retained her powers.
Danger Detection Response: She has the ability to register danger to human life in the vicinity and this automatically gives her the powers necessary to save those lives, be they her own or others.
Situational Biomorphic Adaptation (Nemesis Form): According to the type of danger in the current situation, she automatically obtains the powers necessary to save those lives, be they hers or others. These powers and the forms she takes are determined by the situation she is in and adapts accordingly to the situation at hand. The variety of Lifeguard's power manifestations appear to be almost limitless. Heather becomes aware of how to use any power(s) she manifests after a few seconds. She can also manage more than one power at a time.
Some of her displayed uses of this power are:
Growing Wings for Flight
Extra Arms for carrying and super-strength.
Skin turning into a sort of golden metallic armor
Gills for underwater breathing.
Legs into fish tail for better swimming ability
Upping her strength level from normal to Superhuman
Shi'ar Abilities: Heather possesses some powers constantly after her royal Shi'ar half emerges. These include golden skin, claws, and the ability to grow wings, all when no-one is in danger.
Heather is a trained lifeguard and an excellent swimmer. Other abilities may appear as a result of her changing form.
After being in space her shapeshifting DNA brought out her natural Shi'ar heritage, granting her clawed hands and wings along with the Shi'ar eye markings.
Variable. When her powers are not active, normal athletic human/Shi'ar levels.
It is presumed her mother was a royal Shi'ar due to distinguishing royal marks seen when encountering aliens led by Khan.