Regulus

The creature takes the shape of a lion coated in turquoise fur, its mane and tail tinted a pale rose. Large red eyes dominate its face, and small clusters of that same rosy fur sprout at the back of each paw.

As a summoned attack beast it displays little beyond raw ferocity. It barrels toward whatever target it is pointed at and answers to no one but Nephrite, who calls it into being and banishes it again at will.

Poring over the stars, Nephrite discovers that Sailor Moon's one vulnerability is her devotion to Tuxedo Mask. Seizing on this, he masquerades as the masked ally and mails love letters to the young women across the Azabu-Juban district. When Sailor Moon shows up at the Shinjuku MS Department Store to rescue Naru Osaka, Nephrite channels the star Regulus itself to birth the lion from its namesake constellation. The monster lunges as Tuxedo Mask arrives, and Moon Tiara Action merely glances off it. The two duck into an elevator, which is precisely the snare Nephrite laid, and once they are caught he withdraws the beast. Regulus stands out as the only monster of the day the anime never actually defeats.