Lyse is an enigma. It is unclear just exactly who she is, or whose side she is on. Though it is implied she fights for the Light, she seems to have mysterious ulterior motives that somehow involve Della Tay.
She seems to have a strong connection with solar Light, as she engulfs an entire house in flames, and she appears to be learned in ancient fighting styles, including shurikenjutsu, as she keeps several throwing stars hanging from a string around her neck. It goes without saying she probably knows how to use the katana she keeps on her person.
She has long, black hair, an elegant, "Native American" face, and eyes that are a mixture of golds, ambers, oranges, and reds, described as "fire-like".
This character is part of the Dysfunctional Fireteam Universe
Lyse is first seen eating in a run-down English cottage, watching the news report about Uldren and co. after the Black Garden incident. Upon hearing both royals are unharmed, her Ghost engages her in a clipped conversation about what she was going to do next.
He warns her that revealing herself was what nearly got her killed 'last time', and mentions that Avar Sov, Uldren's father, warned her about doing so as well. She reasons that if she doesn't take action, Uldren will continue to pursue Tay, and end up being killed by whomever it is that Lyse is fighting, Lyse having promised Avar to protect his children from this group.
She claims that she will kill Uldren to get Mara to focus on her rather than Tay, should no other option arise. Her Ghost agrees, and they leave, Lyse using her solar Light to burn down the building and her Sparrow, erasing all evidence of her existence.
Lyse first appears in the war room, where Petra introduces her, Variks, Rogers, and Uldren to each other. Lyse is incredibly hostile, especially towards Variks, likely because he is a Fallen. She is sassed back by Padfoot after making a an offensive comment about Petra's history with Guardians and missing eye, and refusing to obey Uldren's commands.
Shortly afterwards, after Rogers takes Padfoot outside for a scolding, she makes a sharp comment about the Ghost's gung-ho personality, to which he responds by trying to fly into her full-speed, thought Rogers holds him back.
Lyse continues to be hostile and stand-offish throughout the rest of the meeting. She is later seen trying to get food, but her sandwich is subsequently stolen by one of Uldren's Crow drones, on his orders.
She is not seen until later, when she, Uldren, and Rogers are lured into a trap by the Fallen. She is shot in the chest with a wire rifle, and Rogers stops Ulren from trying to help, Padfoot reasoning that Lyse could heal herself, as she is a member of the Phoenixsong Order. They leave her behind, and she ambushes the Fallen as they gather to finish her off, incinerating all of them and leaving deep scars in the floor.
She eventually catches up to Rogers and Uldren during the battle in the throne room, ending the fight. When Uldren pulls a critically injured Rogers out of the rubble, he requests Lyse to heal her. However, the Warlock refuses, on the basis that Rogers isn't worth causing herself to pass out due to Light over usage. An enraged Uldren yells at her, before having to begin rescue breathing for Rogers. Lyse turns her back.
Later on, Uldren glares at Lyse from a distance and vows never to trust her, as anyone who would let a fellow solder die like that is someone he naturally hates. She is shown in a similar scene to be watching Uldren, thinking about how he looks like his father. Foxtrot, her Ghost, comments that Uldren needs to choose a side, and she agrees.
A flashback later shows what appears to be a younger Lyse luring Avar Sov away at knifepoint, only to be stabbed by him, as he thinks she is one of Tay's agents. This is revealed to be a mistake, as her Ghost appears, stating the hostilities had been fake as the Warlock lay dying. She uses her solar Light to heal herself, though with great difficulty, a far cry from her instantaneous flame battle in the transport station, and refuses further medical treatment, asking Avar for help.
Lyse and Uldren are, more than often, seen yelling or arguing with one another. It is mentioned that she once had a close friendship with his father, and she appears to care about him and his sister to some strange, slightly cold degree, willing to kill Uldren if it meant Mara would abandon the Tay search in favor of catching Lyse for revenge.