As the Greil Mercenaries do work, Mist does all she can to assist them; including doing laundry and cooking meals (despite testimony from several characters, specifially Ike, stating that her cooking is atrocious), though not a mercenary herself. Mist herself dislikes fighting, but most likely understands that it is her family's livelihood, so she wholeheartedly supports them.
When Ike trains with Greil in hopes of becoming a mercenary, she goes to meet them, and her entrance allows Ike to launch an attack on Griel that Greil easily dodges and knocksIke out. Mist then tenderly places a wet towel on his head and waits for him to wake, picking flowers. Mist then assists Ike in his training, giving him a vulnerary and cheering Ike on. Sometime after this, she and her friend Rolf, another younger sibling of the mercenaries, leave the fort to pick flowers and are kidnapped by bandits. They are quickly rescued by Ike, Titania, and Rolf's brothers Oscar and Boyd.
Soon after, Soren comes to the mercenaries with news that Daein and Crimea have entered a war, and a woman is brought to the mercenary fort, who reveals herself to be Princess Crimea, and the mercenaries decide to assist her in her flight to Gallia for assistance. Mist packs with Elincia, and Mist shows Elincia her bronze medallion. On the way to Gallia, Mist, Rolf, and Elincia take an alternate route from the mercenaries to avoid fighting, and they reach Castle Gallia first. After joining up with Ike and the rest of the mercenaries, Mist accompanies them to an abandoned fortress in Gallia where they stay. That night, her father is killed, and Mist is devastated by the loss. When the fortress is laid seige to by Daein troops, Mist rushes onto the battlefield, afraid to be separated from her brother. They are then saved by Lethe and Mordecai.
Mist is heavily impacted by her father's death, as he died when she was elsewhere. Determined not to make the same mistake with Ike, she forces Rhys to teach her how to use a Heal Staff, and makes plans with Rolf to fight alongside their siblings. When the Greil Mercenaries move to enter battle again, she and Rolf force their way onto the battlefield and convince Ike and Boyd to let them fight alongside them. From then on, Mist enters battles with the rest of the mercenaries. Mist continues to carry her bronze medallion throughout the war, and she stays close to her brother Ike, growing strong and determined. She voices her opinions on many things to him, such as the laguz and Begnion's aristocrats, and making good friends such as Jil Fizzart. Mist helps uncover Duke Tanas' plot and witnesses the rebirth of Serenes Forest by the Herons Reyson and Leanne with Ike.
Later in the war, Mist's medallion is stolen from her as she sleeps. She is higly distressed by this, because she carried it as a momento to her lost parents. She then learns of its true nature, and the truth behind her Mother death by her father and her Father's death by the Black Knight. When Ike goes to fight the Black Knight in Nados Castle, Mist charges in with him, and she assists him defeat the Black Knight. They then flee from the castle before it collaspes on them.
Mist discovers that the Medallion was stolen by Nasir, and she forgives him after hearing his reasons. She continues fighting with the army and assists in the defeat of Mad King Ashnard. After finding the Medallion in Castle Crimea, she returns it to the Herons, it's rightful owners. She also sings her lullaby, the galdrar of release, to Sephiran, who assures that it will be passed to the apostle; the only one who can release the dark god.
After the war, the Greil Mercenaries reform, and Mist works a few low paying odd-jobs with them for the next three years. As Crimea falls into a civil war, the mercenaries then take on a job from Bastian saving Lucia from being hanged, and Mist and Rhys to their best to rouse her from unconsiousness. Soon after this, the mercenaries take on another job - assisting The Laguz Alliance in their war against Begnion. Ike breifly tries to discourage Mist from coming, but she is still determined to stay with her brother and the mercenaries. Mist then fights with the armies, even going as far as sneaking into a Begnion town with Lethe and Lyre in a cloak to distribute food to the guards that makes them fall asleep.
As the wars continue, Mist grows sick as Lehran's Medallion reaches a critical state. In the middle of a battle with Dain, Mist collaspes and Boyd and Ike lead her off the battlefield. Mist then weakly tells Ike that she hears a voice in her head telling her that the dark god sealed in the Medallion will awaken, and that it cannot be awakened with war, but instead with the galdrar of release. She tells Ike, Tibarn, and Nailah that the apostle must sing the galdrar of release to the medallion before collasping again. When the dark god is released from the medallion, she wakes, and cannot remember what happened.
Soon after, Mist and Ike discover that all of the warring armies have been turned to stone. Yune then decides to talk to Mist - in favor of talking to Ike - saying that Mist has some of Ashera in her, whom she likes. Mist presses her for a way to save the petrified soldiers, and she agrees to help Yune. She joins the Griel army party and finds a Holy Crown that grants her power. Mist enters the Tower of Guidance with the army, and when the Black Knight appears, she lets Ike face him by himself. After Ashera is defeated, she returns to Crimea with her friends.
Super Smash Sisters
Mist is a playable beorc in Super Smash Sisters. She is fast but though her Florete sword can't match Ike's Ragnell or the Black Knight's alondite, her healing skills and not only heal herself but also her allies in battle. She is automatically available.