|Name in Japanese||タナトス・エロス|
|Romaji Translation||Tanatosu Erosu|
Thanatos Eros came from the planet, Evil Star. Her homeworld and Pretty Star, Comet-kun's homeworld has been in conflict for decade. Dark Witches find humans as ideal vessels especially those with innocent heart so they desire to take over Earth. As a Dark Witch he choose an innocent human host, a baby, as her vessel to gain vast amounts of dark magic. Thanatos is the main nemesis of Meruru.
In the Animated Commentary, where she guests in, she was depicted to be a pervert hater by being angry with Kyousuke. She making judgemental assumptions on Kyousuke, who she thinks is doing questionable things with Kirino such as staying in a hotel room with Kirino in Episode 7.
Stardust Witch Meruru 3rd ImpactEdit
In the preview of the 3rd season of the magical girl anime, Thanatos was visible in the background when Meruru turned into a dark witch implying that she maybe somehow responsible for Meruru's transformation.
Kyousuke suggested Ayase to cosplay as her in episode 10 in a bid to win a Meruru figurine in a cosplay competition but Ayase rejected his idea because Thanatos' outfit was too lewd for Ayase. In Season 2's Episode 11 a creative depiction between the tension between Ruri and Ayase, Ruri became the Queen of Nightmare and Ayase became Thanatos. The two fought in a swords fight until Kyousuke interupted them.