Lady Dante is the once lover of Van Hohenheim 400 years ago. They created the Philosopher's Stone and she possess bodies of others to extend her own life.
Many if not all are fooled by Lady Dante's appearence she often if not always chooses young and attractive bodies to house her soul. She like Edward Elric and Izumi has seen the Gate. However her alchemic skill is of a much higher aptitude. She like Hoenheim does not have to touch the surface of the object she wishes to transmutate. Meaning she can create an alchemic current in her hands by clapping and and run it through her body and connect it to watever she wishes to transmutate through touching the floor with her feet. Her alchemic skill is so great all but Greed fear her. She is also Izumi's teacher in alchemy.
Lady Dante's orogins began nearly 400 years ago. She was Hoenheim's lover. And supposedly they had a child together meaning they could have been married at one point. After their child died from Mercury poisoning Hoenheim learned the secrets to human transmutation and attempted to bring back their lost son. The attempt failed and the very first Homunculus was born, Envy. Some time later Hoenheim and Dante researched the theory on the philosophers stone. Eventually completing their research Hoenhein concluded that humans were the needed ingrediants to make the stone. Gathering those sentenced to death in the witch trials and those dying of the plague Hoenheim crafted and perfected the first philosophers stone. But the transmutation had taken it toll on Hoenheim's body and he was dying. Desperate to save his life Dante affixed his soul to the nearest person, and it was then that they discovered immortality. By switching bodies each time the last one began to age they were able to cheat death. Not long after making the stone Hoenheim left Dante (Envy claims it was because he was ashamed of making him) left Dante side leaving her only a shard of the stone.
It wasnt long afterwards that both hoenheim, Dane discovered that their bodies were begining to rott. Dante fearing this tranferred her soul into a newer body to her dismay the process of rotting simply accelerated itself. Hoenheim left his wife Trisha and his children in order to do research as to why his body was rotting. And disapeared from the Elric brothers life for a majority of their youth. Hoenheim discovered that the reason both their bodies were rotting was due to the fact that every time they transferred to a new body they left behind a little piece of themselves in their previous body eventually the soul was left with so little that it lacked the strength to maintain a body.
Feeling that humans were imputant and that she herself was no longer human, Dante sought out other Homunculi to assist her in creating a new stone. After Hoenheim left, Dante had a yound lover. However, due to some unexplained incident he died. Desperate to bring him back she performed human transmutation and created Greed. However like his name suggest Greed was greedy as hell, looking out for only himself. He wanted wealth, fame, power, woman,, and above all that: immortality. For his rebellion, Greed was sealed away by both Dante, and Envy. After the Elric brothers created Sloth, she offfered Sloth some of the red stones, and maintained her. Dante also created the Homunculi Gluttony, Pride. She claims that Pride is her greatest masterpiece a Homunculus that ages yet possess near imortality. She also sought out Lust, and sent Envy to recruit Wrath.
While hoenheim was away Dante did research on the gate and its origins. She discovered that a piece of te gate exist in all of us. When were born out bound with the gate is nearly unbreakable and that as we grow older we become more attached to this world and less aware of the gate. but by using some one of great youth such as a baby the gate can be summoned fourth.
Originally Dante appeared as an old woman living in a mansion in the forest. She took in Lyra as her apprentice when Greed attacked the mansion to retribute for sealing him away it was believed she was murdered by him. However her body wasnt split in half by him but rather by the soul transfer. It turns out that Dante had transferred herself into Lyra's body now Dante's body. Shortly after a series of events Dante took in Rose and her baby, but what she was really doing was preparing for her next vessel as Lyra's body was rotting to the point that without the philosophers stone she woulve rotted away within weeks.
When Gluttony was strucken over the death of Lust and refused to eat away Al's body wich at the time was a philosophers stone lady Dante gave him comfort, or so it seemed she quickly grabbed hold of his tongue and released his oroboros seal. Without he became a mindless creature with no active consciousness he was pure Gluttony. As he started to eat Alphonese away, Alphonse transmuted Gluttony's lower jaw away. After using the stone to bring Edward back to life with his normal limbs, it seemed that the stone was lost forever. On her way up using the secret elevator that connected to Pride's office, Gluttony began to eat his way through the floor. Dante told him to stop but he did not listen as he had no mind. Now he attacked Dante and Dante clapped her hands. When the elevator door opened, both of them were gone.