The filament heart is a large, anomalous object — approximately one and a half to two metres in its longest dimension — that washed ashore on the Dorset coast after a vicious storm, killing and rapidly decomposing wildlife in its vicinity. It is heart-shaped and composed of tightly woven filaments rather than discrete matter, with a weight that varies depending on how it is measured and which way it is oriented — a property that defies normal physics. PISCES designated it the filament heart and established a containment facility in a Weymouth industrial estate warehouse to house it.
Hanover identified the object as fundamentally similar in nature to a meteorite she previously encountered at the Church of the Twelve Martyrs — the same sense of profound wrongness, but much larger. Hex perceived anomalous movement and soft sounds near it, distinct from his Azathoth experiences. Haze theorised the filament heart is the 'anchor' referenced in the decoded cipher message, and that its disturbance by the Deep Energy Project's turbine footings caused the current crisis. This theory gained further credence during the Oasis of Whispers battle, where Haze observed tentacular root-structures withdrawing into the ground, composed of the same material as the filament heart.