Flechette
<infobox> <title source="name"><default>Flechette</default></title>
<image source="Image"></image> <image source="image"></image> <group><header>Basic Information</header> <label>Civilian Name</label> <label>Aliases</label> <label>Gender</label><default>Unknown</default> <label>Death</label> <label>Age</label><default>Unknown</default> <label>Post-timeskip</label> <label>Ward start</label> <label>Relations</label> <label>Family</label></group> <group><header>Professional Status</header> <label>Occupation</label> <label>Classification</label> <label>Unique Features</label> <label>Alignment</label>
<label>Status</label><format><label>Location</label> <label>Teams</label> <label>Previous Team(s)</label> <label>Base of Operations</label></group> <group><header>First Appearance</header> <label>Worm Debut</label> <label>Ward Debut</label></group> </infobox>
Flechette or, as she's later known, Foil is a young woman whose powers can harm even an Endbringer. She is in a relationship with Parian, and they are both members of the Undersiders. Foil joined (and changed her cape name) immediately after Skitter left and surrendered to the Protectorate. Previously, she was a member of the Wards (having transferred into Brockton Bay from another Wards group).
Powers
Flechette's powers let her imbue objects with the ability to penetrate any substance. She can even damage Endbringer cores (which not even Armsmaster's nanothorns could do). We later discover that her power creates duplicate objects in all dimensions, and that this was a shard that was created by the Entities to battle each other.
Warning: this is a major spoiler for the very last arc. During the final battle, Foil hits Scion with a bolt and it opens a gate to where he stores his shards. This is what allows humanity to triumph - the tinker cannon created by the Tinkers that Khepri controls is able to damage Scion directly, and it destroys the remainder of his mass. Scion thinks it so dangerous that prior to the successful shot, he used his 'win power' (similar to Contessa's power) to always avoid being hit by any of her attacks.