Sensor threads are thin strands, barely visible without proper detection, scattered by the leader of Arachnophobia in the Amazon basin.


While the thick foliage of the Amazon allows Arachnophobia to keep the location and entrances to its headquarters, Baba Yaga Castle, such foliage also allows potential threats to move undetected through the forest as well. Therefore, Arachnophobia spread these sensor threads like a web, appropriate for the spider witch, such that, upon being tripped, the sensors alert Arachnophobia of the location of potential threats to eliminate before they come too close to Baba Yaga Castle.[1]

To monitor all of these sensor threads, Arachnophobia has multiple members in Baba Yaga Castle's Security Operations Room to look at a map of the Amazon basin, with Baba Yaga Castle in the middle of this map. Should any sensor thread be tripped, the thread appears on the map as a blinking dot.[2] In cases in which multiple threads are tripped, Security then may turn on alarms throughout portions of Baba Yaga Castle to warn Arachnophobia members to take appropriate actions, which may include leaving the castle to arrive at the location of that threat.[3]

To prevent their opponents from mapping out the sensor threads to avoid being detected, Arachnophobia reconfigures this network of threads every few days so to change the location, number, and frequency of sensor threads; therefore, even if the location of threads was leaked by moles within Arachnophobia, such intelligence would be outdated rather quickly.[1]

Soul Eater Chapter 48 - Baba Yaga Security Operations map

Baba Yaga Castle security operations map identifies Black Star tripping multiple threads

Sensor threads are more easily bypassed by limiting the number of persons passing through the Amazon basin[1] or locating a space where such threads are not present, such as an abandoned mine shaft.[1] Medusa Gorgon was more adept than her Shibusen students at spotting these threads, whether due to her familiarity with her sister's magic technology or her prior knowledge of where each thread was located.[4] Another way to avoid detection by the sensor threads is actually to be detected by those threads—to trip multiple ones at incredible speed until it appears that the person is in multiple places at once, but only a few persons such as Black☆Star possess such speed.[2]


  1. 1.0 1.1 1.2 1.3 Soul Eater Volume 12 Yen Press English translation: Chapter 46 Page 54
  2. 2.0 2.1 Soul Eater Volume 12 Yen Press English translation: Chapter 48 Page 164
  3. Soul Eater Volume 13 Yen Press English translation: Chapter 49 Page 7
  4. Soul Eater Volume 12 Yen Press English translation: Chapter 46 Page 72