|Blood Fort Andromeda|
|Title:||Outer-Seal, Blood Temple|
|Transliteration:||Tasha Fuuin Senketsu Shinden|
|Maximum number of targets:||500 people|
Blood Fort Andromeda: Outer-Seal, Blood Temple (他者封印・鮮血神殿, ?) is the Temple of Blood that surrounded the Shapeless Isle that was the home of Medusa and her sisters, turning it into a palace of darkness, dyed crimson from blood, where the sun didn't shine. Rider is able to implement it as a bounded field that she uses in order to collect magical energy by converting live humans into blood and organic ooze. Using her blood as a material component, she sets up a number of sources around an area to slowly build up energy without leaving a single trace of her existence. It is impossible for Rin to completely destroy it, as new sources constantly appear and old ones are restored. She can only delay its operation date by constantly removing as many sources as possible. It takes over ten days to completely store enough energy to activate that full power of the field, but it can still be activated at any time once the foundations are complete. It damages the leylines of the area once it is completely set up, so it cannot be reactivated on the same land continuously. It leaves a general listless feeling around the area, and Shirou senses the barrier by seeing an image of the area covered with membranes and the people looking like empty dolls while smelling a sweet honey of an insectivorous plant.
Once activated, it forms an advanced bounded field almost on the level of sorcery. It creates a crimson dome-shaped barricade resembling a gigantic red eye around the area of operation, and tints the area in a crimson red that makes a person think that blood is seeping into their eyes. The barrier acts like a separate plane that completely cuts the affected area from the rest of the world, which makes it impossible to see the barrier from the outside, cuts off escape routes for fleeing enemies, and Rin is left unable to contact Archer. Victims within the barrier are dissolved into blood as if they were inside a stomach, and their magical energy is given to Rider or her master. Those with a proper amount of magical energy are able to resist the bounded field, such as a Servant or proper magus, but those without any are instantly drained. If the bounded field is activated without the proper energy, it can take up to a number of minutes to completely dissolve the victims. If Rider has a stronger master, such as when switching from Shinji to Sakura, the effect of the field will also become stronger. It is completely controlled by Rider, and it will continue to stay active even after she dies. It will only be deactivated by her own will or once her body dissipates.
Those under the effect of the weakened barrier almost instantly collapse unconscious and begin to convulse and foam at the mouth due to the dense air. Stronger people can resist for a small amount of time, while weaker people will instantly have their skin start to melt, have inflammation resembling a keloid, and their eyes will look like those of a dead fish. Those closest to the origin of the barrier will suffer the most severe effects, such as their blood being instantly vaporized and having the look of pale wax dolls piled like corpses. Someone with a slight resistance, such as Shirou, will feel instant discomfort as if their senses were revered, nausea, dizziness, a sensation of being extremely hot, and they will have trouble breathing as if they oxygen had suddenly dissipated. If the barrier is removed quickly enough, those furthest away from the from the origin will wake up as if they were sleeping and get away with a stay in the hospital for what amounts to severe malnutrition and slight memory loss. Those closer to the source will suffer from side effects from having their life force drained, scars and necrosis on the tips of the limbs from the melted skin, physical disabilities, such as being on the verge of blindness, and mental scars from oxygen deprivation.