Sloth Online is the sixth episode of the Seven Mortal Sins anime.
While she attempts to contemplate a strategy on how to confront her next adversary, Belphegor, Lucifer is drawn into a virtual world created by the Demon Lord of Sloth inside the Internet, where Belphegor challenges her in a multiplayer online game for world conquest. When Lucifer proves too tough for her and her followers to handle, Belphegor traps Maria inside her virtual game world as well and tricks her into becoming her lingerie-armored champion.
After some laborious training and receiving a special set of armor, Maria (who realized the truth in meantime) - manages to defeat Lucifer, but refuses to finish her off. This allows Lucifer to recover and use her magic to destroy the fabric of Belphegor's virtual world, and with her power diminished by the desertion of her followers as they unlink themselves from the game to pursue matters in the real world, Belphegor is plunged into defeat.
("Numbers indicate order of appearance")