1840 — Mariana is the last child born to William and Octavia Lestrange.
1844 — At an early age, she grew attached to Olivia, more so than to her other siblings. The hero-worshiping phase passed quicker for her than in most children and by the age of four, she no longer adored her sister like an awed puppy but as more of an equal. Around this time, she showed her first display of magic when she managed to magic herself up a tree after having been told she wasn't allowed to climb trees.
1848 — Olivia left for Hogwarts, much to Mariana's displeasure.
1849 — Mariana found a wild grass snake but was forbidden from keeping it. Not content with being denied snake-keeping permission, she decided to keep it in secret. Others soon followed. When her governess discovered her slowly growing collection of snakes she was keeping, she was scolded quite severely and her snakes released back into the wild. In an effort to encourage her into other hobbies that were more ladylike, she was taught flower arranging. She initially disliked it and refused to cooperate but upon learning more about magical plants and flowers that were poisonous, she warmed to it.

1851 — Mariana was finally able to join Olivia at Hogwarts. She had assumed that like the majority of her family she would make Slytherin, she was consequently surprised when she made Ravenclaw.
1852 — Her mother passed away. Being her first experience of death, it came as a great shock and she was deeply upset by the loss.
1855 — Mariana is made a prefect.
1856 — Mariana decides to take a particularly heavy load of NEWTs, reluctant to drop a good number of her classes claiming to do otherwise would be to render herself ignorant.

1858 — It was at her Coming Out Ball that she first met her fiancé and she decided instantly that she didn't like him. Nonetheless, she had no emotional attachment to any other eligible bachelor and while she was not the most obedient of the Lestrange girls, she knew better than to put up a fight. Her sister had a reasonably happy marriage did she not? In the winter, she married Eustace Macnair and found that married life did not suit her and so she endeavored to spend as little time with her husband as was humanly possible by involving herself in hobbies.
1861 — Mariana avoided marital duties as much as possible and consequently it took nearly four years for them to have a child. Fortunately, it was a boy meaning her obligation to give her husband a son was done with. Mariana insisted on naming him Valerian after the plant.
1862 — Her interest in venomous creatures eventually brought her into the path of Mr. Oswin Bennett who was a breeder of exotic animals. A few meetings after their initial acquaintance, an affair began. At the time she almost fancied herself in love with him but the reality was, she was only in love with the risk, the escape and the rebellion of it.
1864 — She carried on in this way until it became clear that she was with child. Shortly after, her lover turned up dead. To this day she doesn't know who killed him. By December she was the mother of a pair of twin boys. Her husband seemed to turn a blind eye to what she had done despite it being quite obvious they weren't his.
1865 — As a way to spend even less time with Eustace, she took up a job at St. Mungos as a Healer. It was certainly frowned upon and Mariana had known from the start that it would be, but she didn't particularly care. She despised her husband and if that irritated him then all the better for her.
1868 — Yarrow was born. It is at this point that Mariana realized she wants a daughter instead of more sons.
1871 — Germander is born. Mariana is irritated at this point by her many sons.
1872 — Sage. Another boy. Mariana started concocting poisons and antidotes of her own devising in her spare time. To take away some of the disappointment of having yet another son, Mariana dressed Sage as femininely as possible.
1875 — Tybalt is arrested for murdering some people Mariana didn't really care about. Her main concern is his only daughter whom she insists on taking in. Oh and Klaus died.
1877 — Tatiana leaves for Hogwarts. Mariana was very displeased at the loss of her pseudo-daughter to school.
1878 — Mariana transfered from St. Mungo's Hospital to Hogsmeade Hospital, she was shortly thereafter promoted to Assistant Head of Potions and Plant Poisoning. The Macnairs moved to Hogsmeade.
1879 — Mariana could no longer keep Sage in girls attire full-time without it being strange. He would still occasionally get shoved in a dress for her own amusement when really bored, however.
1882 — In May she was drafted for the Hogsmeade Trail. Mariana reached the end of it unscathed but was then held prisoner by muggles, much to her disgust. She did not return home until August. Afterwards, Mariana was promoted to Healer-In-Charge of the Potion and Plant Poisoning ward at Hogsmeade Hospital. She also stopped dressing Sage like a girl - completely. At the age of ten he could no longer pass for a pretty little girl. It was also revealed that Valerian had a bastard daughter. After her return from the trail, Eustace attempted to improve the state of their marriage by winning her affection. Sebastian died.
1883 — A serial killer nearly killed Mariana but she managed to escape, not without losing some pride first though. Mariana's feelings for Eustace were rapidly changing but then a letter from a former mistress of his arrived. The revelation that he had managed to father a daughter with another woman, ruined the progress they had made. Valerian then decided to run off with his bastard and her mother. Mariana hunted him down and upon finding him, she murdered his bastard's mother - whom he had married - and took both him and his daughter back to Hogsmeade. The child was set up as a ward, renamed and obliviated. The entire debacle further soiled her budding feelings for her husband who had no helped her in recovering their wayward son.
1884 — After finding out Yarrow was sleeping around with a low class hussy, she grew concerned he might do as Valerian did and made him take an unbreakable vow. Mariana later discovered she was with child for the first time in 12 years. The Laughing Plague arrived shortly after, Mariana fell ill, Valerian died. Days later, a fire spread throughout Hogsmeade and burned down the house, Marigold perished along with it. Mariana resigned from the Hospital. They did not rebuild in Hogsmeade.
1885 — Mariana finally got her long-desired daughter. She then sent Agrimony and Betony off to get eaten by Quintapeds because of potential inheritance issues. A moment of carelessness by the nurse saw Mandragora drown in her bath later in the year. Mariana murdered the nurse and had something of a break down, not helped by her lack of employment. After much drinking, a threat of commitement to an asylum from Eustace, and the suggestion of trying for another daughter she finally gets her act together. For lack of anything to do, she decides to purchase a shop in Knockturn Alley on the quiet and sell her poisons and venoms from it. She names it Locusta's Liqueurs.
1885 — A basilisk was hatched. Oh shit. Mariana had been trying very casually for a few years to successfully hatch one and then succeeded but sadly had to blind the poor thing so that she didn't, y'know, die.

Mariana is needs to kill that basilisk, and I don't mean that as a penis metaphor.