She first appeared when Sara tries to get an audience with the Queen of Grand Noah for assisiting with the investigations of Esta and the Tartarus Rift in the lake. She interrupts the conversation and says that Luka should prove himself by participating in the Queen's Cup, to his companions' surprise. The party accepts as they realize they have no choice in the matter.
Before the finale, Mephisto reveals her plan to use Luka to attract someone that appeared then according to the true history. After Luka beats Alma Elma, Mephisto shows up and brings in Granberia to capture the Succubus Queen. The latter convinces Luka to join force and managed to beat back Granberia, forcing Mephisto to leave as she recognizes she is completely outclassed.
Acknowledging the foul plays, the queen of Grand Noah asks Luka for a favor and give him the key to access the Magical Academy to find out what Mephisto is up to. Luka and Co then head in, meeting a disguised Alma Elma along the way who notes that Mephisto is talking to someone, and that they might be able to catch her in the act. Indeed, upon arrival to the second floor and reaching the head master’s room, Lilith is there along with Mephisto. She reveals that she in league with the Monster Lord Alipheese the 15th and Lilith states that they're in an alliance of interest. As the party tries to retreat, Lilith block their exit in the blink of an eye before being engage in a fight by Alma Elma, leaving only Mephisto to fight. She notes that while she isn’t as powerful as before, she used to be someone quite feared throughout the land, and transforms into her battle form and engages combat.
One beatdown later, Luka and party bring Mephisto back to Grand Noah before the Queen, expecting her to be punished. However, to their surprise, the Queen allows her to stay as the advisor in return for providing information, since Mephisto has engaged herself to serve Grand Noah's interest to the best of her abilities.
Mephisto then tells the party that there is a conflict in Plansect Village that they should go solve. Alice/Ilias says that Alipheese the 17th ended the conflict however Mephisto speculates that someone has re-ignited the war themselves.
Once the party has checked Esta's Tartarus, Mephisto tells them her plan to infiltrate Grangold: Meet an expert in Lima Village Ruins, then go through Gold Fort while the joined armies distract Grangold's own forces before getting to Goddard to get more support to infiltrate Grangold.
She's later seen at the Toxic Swamp east of Goddard, as she's the magic expert sent by Grand Noah to support Luka. She then proceeds to join the hero and becomes an official party member.
“A confidant of Alipheese the Fifteenth who is also serving as Grand Noah’s magic advisor. Wielding very powerful magic, she knows spells from all eras and regions. Her true form is that of an evil serpent, and is extremely formidable in combat. She is also very cruel and will swallow her prey alive. Anyone who angers her will have their semen squeezed as she preys upon them.
She is very cunning and methodical, but there is one aspect of her that deeply values ancient Yoma traditions, and she is very respectful of contracts and commitments. It appears Mephisto’s devotion to a contract sometimes exceeds even her own loyalties.”
- Attack – One Foe
- Ten Finger Masturbation – One Foe (Luka), Pleasure Attribute
- Ten Finger Masturbation – One Foe (F), Pleasure Attribute
- Snake Tongue – One Foe (Luka), Pleasure Attribute
- Snake Body Strike – All Foes, Physical Attribute
- Mega Fire – All Foes, Magical, Fire Attribute, Burn (10%)
- Mega Blizzard – All Foes, Magical, Ice Attribute, Freeze (10%)
- Mega Thunder – All Foes, Magical, Lightning Attribute, Shock (10%)
- Blaze – One Foe, Magical, Fire Attribute, Burn (10%)
- Frost – One Foe, Magical, Ice Attribute, Freeze (10%)
- Spark – One Foe, Magical, Lightning Attribute, Shock (10%)
- Silence – All Foes, Magical, Silence (75%)
- Death – One Foe, Magical, Death (75%)
- Mass Dispel – All Foes, Auto Hit, Dispel All
- Enchant Magic – One Ally, 150% Magic for 6 turns
- Mephistopheles – All Foes, Magical, Sonic Attribute, Poison (80%), Confusion (80%), Learnable
She’s a spell caster, but has some non-magical attacks. If you can, magic reflect is very good against her, but beware of Mass Dispel, as it will remove it. As a Yoma, she is resistant to Fire, but weak against Ice and Holy. Otherwise, just bring people strong against the magical elements and beat her down. She has rather low agi, so your team should go before her.
“So you ended up as the prey of a female teacher. I think you'd fit perfectly living in modern day Japan... Mephisto is a tough opponent that has various magic at her disposal. If you fight properly, you really shouldn't have much trouble. Ice is very effective against her because she is a lamia. Silence works on her and you will have a great advantage if you seal her magic. Now go on, immoral(and at the same time)brave Luka. If you become more immoral, you will ruin your companion's lives.”