Heavenly Herald Papuu has lower stats than Daboo of the Dead, but is overall harder thanks to having a significantly longer Omni Strike range plus a shorter battlefield in her debut stage, allowing her to hit the Cat Base from afar, as well as faster attack rate. Her attack power is quite low, but she has a new trick up her sleeve: she has the Toxic ability which deals percentage-based damage, so even King Gamereon will die in 3 hits (her ability takes 40% of a unit's total HP). She has the same immunities as her predecessor along with immunity to waves, and her base damage is tripled at 30% HP.
Due to her Toxic ability, refrain from using tanks and slow units against this enemy, as she'll kill them before they do a significant effect in-battle. Instead, use quick units that can rush, such as Fishman Cat, Bullet Train Cat and Awakened Bahamut Cat.