im pretty sure you wanna learn about elluka too ~

here's le http://theevilliouschronicles.wikia.com/wiki/Elluka_Clockworker

Elluka is a powerful sorceress known as the mage of time and throughout the story later on becomes involved with conflicts caused by the sin vessels

[Elluka is hardly ever childish she's always in a serious tone unimpressed by anything unless it involves the vessels]