Dark Mercury is a evil villainess created by Kunzite to fight the Sailor Senshi in Pretty Guardian Sailor Moon.
Dark Mercury first appeared in Act 21 after Ami was kidnapped and brainwashed by Kunzite, She's shows dishonor to everyone in the Dark Kingdom including Kunzite who kept trying to hit on her. But she shows Kindness to Nephrite, When she appears his cape, In Act 25 Akumi greets Sailor Moon and transforms in Dark Mercury and battles along with Kunzite during the fight Kunzite knocks Sailor Moon down with a strong final blow, Dark Mercury angrily tells Kunzite that Sailor Moon was her Prey, But Kunzite told her that " Today is Different" and waves his sword at Sailor Moon preparing to attack her until Tuxedo Mask jumps in and saves Sailor Moon by taking the attack himself which causes Sailor Moon to break down and cries as Kunzite and Dark Mercury argue with eachother Sailor Moon transforms into Princess Serenity using the power of the Silver Crystal to heal tuxedo mask (Endymion) Eventually Dark Mercury along with Luna were both bathed into the Silver Crystal's light which caused the Shitennou to retreat. In Act 27 Dark Mercury was seen battling a unknown Sailor Senshi on a tall buliding the unknown Senshi noted the spell that was placed on Sailor Mercury started to Weaken as the Senshi welds her Moonlight stick which gives a off a bright pink light, as Dark Mercury shields her eyes the light fades as the unknown Sailor Senshi vanishes into thin air her voice echos saying : Mercury, I'm sure you'll be back,the mysterious senshi was seen walking down the street, and then pauses, and exclams with delight, and then skips off- transforming into Luna in mid-stride, Later Dark Mercury was still on the tall building, Staring into the distance and started to remember herself as Ami, Dark Mercury was confused trying to remember who she is. Later at night at the Dark Kingdom Dark Mercury stands by a pond, watching as the Moon reflected in the water, and grabs her head as all her memories returns as Kunzite appears he throws a rock in the water that disrupts the reflection, and orders Mercury not to look and tells her that she is already part of the darkness. The next day at the Secret Base as the Senshi were trying to figure out who the mysterious girl is Usagi revises a phone call from Dark Mercury on her Teletia S telling her that she wants to face her alone, Usagi lies to Rei and Makoto and tells them that Ami wants to meet them at the Mokuba amusement park as the 2 Senshi rush off to the amusement park, Usagi goes inside a large huge building to face Ami alone declaring that she'll save Ami and bring back. As huge battle emarges between Sailor Moon and Dark Mercury a strange girl interrupts and tells Sailor Moon that she overheard the phone conversation and pulls out a phone and transforms into Sailor Luna and challenges Dark Mercury until Kunzite appears and told Sailor Luna that he'll be her opponent but unfortunately Kunzite was to strong to her Sailor Luna was defeated and was changed back into her cat form. As the battle continues Sailor Moon tries to reach out to Dark Mercury by calling her Ami-chan which causes Dark Mercury to alter more memories as she steps back she attacks Sailor Moon, Realizing that Ami is returning to normal and is in pain Sailor Moon's Brooch glows a golden light a image of Ami appears calling out to Usagi, but Kunzite uses dark energy to blast the image of Ami away and tell Dark Mercury to stay firm, as Dark Mercury stands up to attack with her dark sword Sailor Moon uses her Moonlight to block the attack, the attack shatters the stick instead causing Sailor Moon to Collapse as Dark Mercury watches with a Staisfed smirk of her face. But all of sudden her smile fades as all her memories return realizing what she has done Mercury drops her sword and rushes over to Sailor Moon's aid as she watches her friend in horror she throws back her head and screams. Act 27 was the last appearance of Dark Mercury.