Ivy the Poisonous Mass is an optional boss in Core Kepper. While not part of the main story quest, it’s certainly worth a challenge as it drops Poisonous Sickle, arguably the best weapon in the game. However, finding the boss is not easy and may take a while. Additionally, it’s one of the more challenging bosses in the game, so be prepared before you engage in battle.
How to defeat Ivy the Poisonous Mass
Ivy the Poisonous Mass can be found in the wilds of Azeos. It doesn’t have a fixed location and you’ll have to keep looking until you find it.
Take the entire Scarlet armor set for the battle. While not necessary, carry the Swift Feather for extra movement speed, which can be beneficial when fighting the boss. Aside from that, pick up a Remedaisy Necklace for immunity to poison, a Form Ring for extra critical hit chance, and a Celestial Ring for extra critical hit chance and melee damage. Finally, use Ruin Song as your main weapon.
Before you start the fight, make sure you’ve cleared the walls around them so you have more room to play. Also, remove any poisonous slimes on the floor beforehand. Once you’re in the fight, just hit them and keep running in a certain direction. Every time she attacks, she will jump out of her spot, giving you a chance to hit her. Continue the hit-and-run method until all of her health is depleted.
https://www.gamepur.com/guides/how-to-defeat-ivy-the-poisonous-mass-in-core-keeper How to defeat Ivy the Poisonous Mass in Core Keeper