Kendra Saunders was a young woman who committed suicide. When Kendra's soul left her body, that of her grandfather's first cousin Shiera Hall, the Golden Age Hawkgirl entered it, making Kendra a walk-in. Her grandfather, former OSS agent and globe-trotting adventurer Speed Saunders, recognized this, in part due to a change in eye color, and encouraged his granddaughter to embrace her destiny as the "new" Hawkgirl.
Kendra had a daughter named Mia, who is said to be deceased.
Still believing herself to be Kendra, she debuted as a hero using the original Hawkgirl's equipment and set out in search of a being called the Fate-Child (actually her own reincarnated son, Hector Hall). This led to a meeting with the Justice Society and Kendra's induction to that team.
She currently has all of Kendra's memories, but almost none of Shiera's save for fighting experiences. This creates tension with Hawkman since he remembers all of their past lives together and believes they are destined for each other. Kendra has been presented as a very troubled young woman, haunted by the murder of her parents by a corrupt cop and confused by her jumble of memories and feelings. She has operated as Hawkman's partner but only recently began to actually admit her attraction to him. The truth about Kendra's identity was eventually revealed to her by the angel Zauriel.
She is one of the heroes who fought in space during the Rann-Thanagar War. Following the events of Infinite Crisis, a Zeta Beam transporter malfunction injured many of the superheroes in space, including Hawkgirl, causing her to grow over twenty feet tall. Some time later, her proper stature restored, she is protecting St. Roch, Louisiana, in the absence of Hawkman. She was later abducted and put on trial for high treason against her people by a group of rogue Thanagarians. After being found guilty, one of the rogues tied her hands behind her back and covered her mouth with a piece of duct tape, and then attempted to lynch her. Kendra found that she could hover without her wings and was able to fake her death and escape by using this new power.
She is also a returning member of the new Justice League, having briefly served with the team when the original members were previously missing. A brewing relationship between Hawkgirl and Red Arrow become one of the major subplots in the series though it appears to have ended. Hawkgirl is now 100% Kendra Saunders. Shiera Sanders' soul left Kendra's body and moved on to the afterlife. Shiera hopes her passing on will finally remove the curse of Hath-Set.
Hawkgirl owes her powers to a belt of Nth metal, a substance native to the planet Thanagar (once home of another pair of Hawk-heroes, Katar Hol and Hawkwoman). The metal is psycho-reactive, responding to its bearer's thoughts and in its base form has a number of electromagnetic/gravitational properties. To the Hawks, it grants the power of flight, superhuman strength, super-acute vision, and an enhanced healing/regeneration ability.
Additionally, she displays advanced hand-to-hand combat skills. Like Hawkman, she retains the knowledge of several lifetimes worth of fighting. Her preferred weapons are a spear or mace, but she has also been depicted using swords, axes, warhammers, shields, and other melee weapons. She possesses shooting skills from her times as the gunfighter, Cinnamon.
In addition, the Nth metal knife which murdered Hawkgirl in her original incarnation as Chay-Ara had an unusual effect upon her soul and that of her lover Khufu (Hawkman). The pair are locked in a seemingly endless cycle of death and rebirth throughout the centuries. While not a superhuman power per se, this propensity for reincarnation has allowed Hawkgirl to cheat death and return to active duty in her current incarnation.
Recently, Kendra has discovered that she had enhanced healing and limited hover abilities when not wearing Nth metal. She speculates that this is due to her prolonged exposure to the substance. It remains to be seen if she still possesses these abilities now that she is Shiera Hall once again.