WeakWood Throne

Forest Zoz will give you this quest, one screen east and one screen south of Hermit Greg. Lillian will be one screen south from Zoz. She isn't that tough to beat. She will either do three consecutive smash attacks that leave earth ripping up in a line, a lightning strike which will show targets on the ground, or summon a few slimes. The two attacks are very easy to predict and dodge, and the slimes should die in two hits if your strength stat is around 10. You can get in six hits between each of her two damage attacks. Continue this pattern to defeat her and grab the key, then return to Zoz to complete the quest.