The origin of all taratects, basically our MC's grandmother, mother of 2 or 3 other Mothers. Also current holder of the title "Maou".
Appearance wise, a spider girl but not an arachne, maybe more like LoL's Elise.
Gotta give this adaptation (and the original for that matter) credit for always keeping the plot moving. Quite refreshing to not have an arc that rivals the length of Naruto filler.