Heroes Story
Poison Ivy is the boss of the fourth level in episode one: "A Poisonous Appointment." Poison Ivy's goons grow from the ground and attack you while she hides within giant plants. Find Lego pieces near the left plant and use them to build a bomb. When you complete building it, it will explode, forcing Poison Ivy to reveal herself. Build Lego bombs to blow up the remaining two plants to reveal her health bar. Attack her until she's defeated.
Villains Story
Poison Ivy and The Riddler team up in the third level of episode one: "Green Fingers." You use her to double-jump over the railing outside the greenhouse to let The Riddler in and to wade through the toxic pit and create platforms for your partner to cross. Inside the greenhouse, use Poison Ivy to assemble a vehicle made from smashed objects and then later to walk through gas to open a hatch. Inside the laboratory, use her to grow plants you climb to find Lego pieces.
Attacks
Poison Ivy has several offensive attacks that you can use to immobilize or defeat your opponents. Like every other character, press the "B" button to physically attack opponents when you are close to them. You can also press the "Z" button to release a poison pollen. When enemies walk into it, they will become dizzy and fall over. If enemies are close, press "Z" to have Poison Ivy kill them with a toxic kiss.
Abilities
Poison Ivy is immune to toxins, so you can use her to pass through all kinds of poisons such as toxic waste pools and harmful gases. Her toxic physiology gives her added body strength, which she uses to jump extra high. You perform a double-jump by pressing the "A" button to make her jump, and then pressing it again while she is still in the air. This lets you reach certain places in the game that some other characters cannot get to.