Pamela Isley grew up isolated. With her wealthy parents inattentive at best, she had but plants for company of which she cultivated many, vegetables and flowers alike. Time came, and she went to college — to study botany, naturally — and fell in love.

The object of her desire was her professor, Jason Woodrue, who would later become the Floronic Man. Much more intuitive with plants than with people, the romantic Pamela began to trust him — enough at last for her to volunteer as a test subject for his experiments. They were a terrible success — the toxins Woodrue injected into her bloodstream fused with the student's cells, giving her a resistance to poisons — after nearly killing her first.^{[LDK43][SB56]} However, they also made her skin poisonous to touch. Even if she were to trust again, she would never again caress nor be caressed …^[CS]

The massive changes in her body left Pamela in hospital for six months after the experiment. She came back emotionally volatile — one moment sweet, the next destructive —, but also irresistable. She quit school soon after, after her boyfriend totalled his car after a fight.^[LDK43]

She changed her name to Poison Ivy — like the plant, she was dangerous to touch — and came to Gotham to start a new life where she would be the ruthless one. She would no longer be on the receiving end of betrayal. She had tried to play nice; they had violated her. Now, she would get even, with interest. She would beat them at their own game.^[SB56]

Like so many who felt their violation entitled her to be ruthless in turn, she finally encountered the Batman, and developed a burning hatred — and a burning desire — for Gotham's dark avenger^[SB(A)3], the man she could not control^[SB58].

After her rehab, Pamela was accepted for a position at Gotham University, but things soon got out of control when her benefactor started blackmailing her into producing a new drug, "Edenspring." Batman ended up under the influence of her pheromones^[LDK42], but finally saved her life when his head was clear again.^[LDK43] He saved her life again when on a different occasion, Ivy's heavily modified immune system began to break down and he convinced her to seek out treatment before it was too late.^[DC589] It is incidents like these that suggest to her that maybe deep down inside², the Batman is more than just in lust with her.^[SB(A)3]

On their next encounter, Ivy enthralled the guests of a Wayne Foundation dinner with genetically enhanced nightshades. When he recognized Ivy, Wayne was able to secretly use nose filters so he would not be affected like the other guests. He let himself be herded along with the aboulic lot, turning into Batman at an opportune moment. To this Ivy responded by sending a horde of her "Deadfellows" against him, mindless slaves infected past the point of no return. In the end however, the Dark Knight prevailed.^[Bat495]

At one point, Ivy was offered a pardon if she served with Amanda Waller's Suicide Squad, and she agreed, serving for a time alongside the likes of Bronze Tiger, Deadshot, and Vixen, but also making a mortal enemy of Count Vertigo.

As her transmutation progressed and her body became more and more plant-like, her concern for plants and the environment grew. She withdrew from civilization, a hermit who brought life to a barren Carribbean Island, transforming it into a tropical paradise. Soon however, her refuge turned to ashes as ruthless arms dealers used the island to demonstrate the devastating effects of Prometheus, a new brand of Napalm. Homeless and enraged, Ivy returned to the US to wreak revenge on those responsible.^{[B:PI][SFO:Villains]} No longer just a seductress, Ivy turned into an eco-warrior, attacking all companies and individuals who she believed were harming the environment.

Her accomplices however were seldom fully aware of this change of objective, such as baby-food manufacturer Fenn who laced his product with a designer disease created by Ivy in the understanding that they'd be able to charge astronomical sums for the miracle cure later. Of course, this cure never really existed as unbeknownst to him, Ivy had hoped for the disease to wipe out a significant portion of humankind^[TPT] in a plot that anticipated Ra's al Ghul's Contagion.

When the "clench" virus struck Gotham, the Batman "borrowed" her from Arkham to get a potential antidote to the infected locked up in the Babylon Towers, arguing that her immunity to seemingly every toxin and virus known to man would make her the logical choice — she would be safe even if the antidote was a failure. Figuring that there was not enough antidote for all to try, Ivy auctioned off the shots to the highest bidders.^[Bat529] When the cure did not work, she started selling her kisses, promising to pass on her own immunity. Not surprisingly, Batman was less than impressed with the results when he finally went in to see what took her so long,^[SB49] and returned her to Arkham.^[DC696]

Soon afterwards however, she was broken out of Arkham^[SB56] by the Floronic Man who offered her ten million dollars for a blood sample so he could create offspring between the two of them. Ivy accepted^[SB57] but then instigated a fight between the Floronic Man and the Batman when the latter arrived on the scene to put an end to Woodrue's drug trafficking. Batman managed to beat Woodrue, but Poison Ivy got away with her riches.^[SB58] The status of the blood samples remains uncertain.

Ivy's next encounter with the Batman was when she seduced Joe Potato, PI into bringing her the emerald skull of Valejo, an artifact that allowed her to create zombie-like plant-creatures on the spot. Just as Ivy was about to send the creatures to destroy Gotham and its citizens, the skull was destroyed in a fight between Batman, Ivy, and Potato, and so was Joe's relationship.^[SB(A)5]

Her next attempt to give Gotham back to Gaea happened after the earthquake hit Gotham. Hoping to use the general confusion to her advantage, she tried to spread her seeds and super-fertilizer by dumping them in the city's freshwater reservoir, but was thwarted by an absurdly lucky Catwoman.^[Cat57]

Her return to Arkham was but brief however; when Gotham was declared a No Man's Land and the asylum ran out of supplies, the inmates were at last released^[SB82], and Ivy made a home of Gotham's Robinson Park. She cleansed it from years of pollution and turned it into a virtual Eden, allowing only children to seek sanctuary inside.

Her happiness only lasted so long, however. Basil Karlo, the first Clayface, invaded the park, imprisoned Ivy, and used her children as slave labour to harvest and sell produce throughout the starving No Man's Land for six months.^[SB88] With the aid of Batman and Robin, Ivy broke free^[Bat568] and defeated Karlo, using his body to fertilize her plants. Batman managed to coax her into a truce; she would continue growing produce and freely give it to the Gothamers, and he'd leave her in peace.^[DC735]

But Ivy could do better than this hesitant temporary alliance. When Harley Quinn had nearly been killed by the Joker, Ivy found her and saved her life, planting the seeds of friendship. Out of sympathy for the doctor's lot — abused by the man she loved — and reckoning that Harley would not in fact be bound by the truce Ivy had with Batman, Ivy boosted the clowngirl's agility and strength with one of her potions, also granting her immunity to Ivy's poison touch.^[B:HQ]

After the No Man's Land status was lifted, the city fathers of Gotham decided to evict Ivy from Robinson Park. Rather destroying it than letting it flourish in Ivy's care, they threatened to use defoliant.^[DC751] Despite of the Dark Knight's attempts to discourage her from standing up for what she believed in, Ivy decided to go under with the park. When the children refused to leave her to die, Ivy turned herself in to save them.^[DC752]

Once more, Ivy was sent to Arkham. This time however, she would not spend her days pining for the Batman.^[Bat(C)9] This time, she had a friend waiting for her …

Poison Ivy and Harley Quinn are currently at large.

This is the point at which our role-playing game started; from this time on, the story in canon goes one way and that of game goes another.