Regina Mills is the main antagonist of the first season, the tertiary antagonist of the the second season, the tritagonist of the third season, the protagonist of the fourth season, the protagonist of the 1st half of the fifth season, and one of the 8 protagonists of the 2nd half of the fifth season of the of ABC's Once Upon a Time television series. Regina is the Evil Queen whose Dark Curse sets the plot in motion.
Regina is a conflicted and damaged woman whose life has been controlled by selfish and powerful people, first her heart-reaping witch of a mother, Cora, and later by the cowardly cursed sorceror, Rumplestiltskin. Once a sweet caring girl, Regina's heart was shattered with her lover's assassination and hardened by her forced marriage to King Leopold.
Her persuit of magic gave a false sense of control while still being manipulated by Rumplestitlskin into casting the Dark Curse which consumed the Enchanted Forest. When she got Henry she found happiness and unconditional love Regina did not had but her persuit of revenge against Snow White has lead to her nearly loosing her son to dark magic.
Turning to Evil
Regina was born to Henry and Cora. she starts out as a sweet kind caring girl until she falls in love with her stable boy Daniel. Her mother finds out hearing the information from Snow White thus setting in motion Regina hatred for the young princess. Cora kills Daniel by ripping out his heart. After an unwilling marriage to king Leopold Regina finds her mother spell book and unwittingly summons Rumplestiltskin who after disposing of her mother teaches Regina magic. Regina then kills her husband and proceeds to send a Huntsman to kill Snow White. After this failed Regina decided to use the Sleeping Curse upon Snow White but due to Rumples' interference Prince "Charming" David broke it with True Love, the most powerful magic in the world.
In the aftermarth Snow and Charming unite an army to conquer the kingdom and after a long war they manage to defeat Regina's army and use good magic to capture her. Regina was to be executed but Snow lets her go, though after cursing her- the curse prevents her from harming Snow and Charming in their realm.
Enraged and manipulated by Rumple the queen casts the Dark Curse which brings the whole inhabitants of Enchanted Forest to Storybrooke, in the Land Without Magic.
Breaking of the Curse
Twenty eight years later Regina's adopted son, Henry, brings Emma to the town who, after the boy is accidently cursed, breaks the curse. After Mr. Gold brings magic to Storybrooke he attempts to exact revenge on her because she held his true love hostage but the action sents Snow and Emma into the Enchanted Forest.
When they return, they bring Cora to the town. Cora's own manipulations lead to her own death at Regina's hands. Soon Henry is kidnapped by Greg and Tamara, a duo of magic hunters, and brought to Neverland. Peter Pans steals Henry's heart but the boy is saved by the timely interference of Regina and Emma. However Peter gets his hands in the Dark Curse and casts it upon Storybrooke. Regina uses the curses' scroll to break it but it results in everyone being sent back to the Enchanted Forest.