Capella Emerada Lugunica

Capella Emerada Lugunica is a Sin Archbishop of the Witch Cult, representing lust. During the events of the Fifth arc, she acted as one of the main antagonists, alongside her fellow Sin Archbishops.

She is also known as Mother, a mysterious figure who controls "children" (including Elsa and Meili) in a group of sorts that operate throughout the world, waiting for her orders.
(Source: Re:Zero Wiki)