Credits
Author:
Picture: https://search.creativecommons.org/photos/b1f3864c-abbb-454a-ab98-2d2e27cdc0a7
Licence: CC BY-SA 2.5
Notes: I took inspiration to write this SCP from Tanija as one day she simply wrote me "Robin, moray-scp, now".

SCP-227-DE in it's habital containment
Item #: SCP-227-DE
Object Class: Keter Euclid
Special Containment Procedures: SCP-227-DE is to be contained in a size 10 containment cell with integrated habitat adapted to maritime anomalies at Site-DE6. In addition, the cell shall be equipped with an environmental simulation acclimated to the climate of the North Sea zone. Besides the habitat, the containment cell shall also contain a dry area, which shall be used to allow research and maintenance personnel to enter the cell. The containment cell is to be hermetically sealed at all times and is only accessible via an entrance located at the dry area.
SCP-227-DE is to be supplied with at least three liters of bovine or human blood every day. However, it should be noted that the individual phases of the moon have a significant influence on the required amount of blood. In the appendix "Diet plan of SCP-227-DE" the respective regulations can be consulted. Due to the highly cooperative nature outside of a "Blood Night" event1 is allowed to freely set its diet plan for any day once a month. In order to be prepared for the necessary amount of blood, the moon phases are to be calculated at least two months in advance, so that the necessary amount of blood can be provided. However, besides bovine or human blood, SCP-227-DE does not need other food sources to survive.
Should a "blood night" event occur, then Protocol 227-DE/1 shall be executed and maintained for a total of 48 hours. Protocol 227-DE/1 involves evacuating and hermetically sealing the sector in which SCP-227-DE has been contained. In addition, the pool containing SCP-227-DE will be separated from the rest of the containment cell with a retractable 2 cm thick steel plate and hermetically sealed at least eight hours prior to the start of the event. In the event of a successful containment breach, the sealed-off sector will be shock frozen to forcibly transition SCP-227-DE from its sublimated state to its resublimated state and allow it to be re-contained.
Upon discovery of SCP-227-DE-1 instances, they shall be contained and temporarily stored in a hermetically sealed size 3 containment cell for humanoid anomalies. Depending on the nature of the SCP-227-DE-1 instance, the project director shall decide whether to terminate the stored instance by any method or transfer it to Site-DE18 for research purposes.
Description: SCP-227-DE is a female entity belonging to the genus Mureana (moray eel) and resembles the Muraena augusti (black moray eel) in appearance. In contrast to the common Muraena augusti, SCP-227-DE has a total body length of 3 m and a total weight of 11.43 kg. By means of several magnetic resonance tomographies, for the determination of the age of SCP-227-DE, it has been determined that it must be at least 1100 years old, which means that its origin can be dated to about 920 BC. In addition, it is capable of extending the pharyngeal jaw found in common Mureana up to 150% further than should usually be possible.
Morphological and molecular genetic analyses suggest that this specimen is a distinct subspecies of Muraena augusti, as previously unknown gene sequences were found. With the discovery of a possibly anomalous species of Mureana, SCP-227-DE's species was given the scientific name "Mureana ne usitatus augusti" and included in the Handbook of Paranormal and Anomalous Marine Species. So far SCP-227-DE is the only specimen of its kind known to the Foundation, but explorations regarding further conspecifics are currently waived. Since SCP-227-DE is a female specimen, mating attempts were made with common male Muraena augusti. Up to the actual fertilization the attempt proceeded without complications, but after the mating it was discovered that SCP-227-DE is considered infertile.
One of its anomalous characteristics is that it can sublimate and resublimate at will and at any time. Should it change to the sublimated state, it appears as a black gas that can move freely. While in this state, it cannot interact with any other life forms. However, SCP-227-DE does not appear to be able to maintain this sublimated state for more than three hours at a time. In addition, it can move as fast as 15 m/s in the sublimated state. When SCP-227-DE is resublimated, it can also re-manifest above water and survive above water for a period of 45 minutes.
Prior to Event 227-DE/13 the nature of SCP-227-DE was strongly hostile, aggressive, territorial, and it showed no signs of intelligence or empathy. Despite the fact that it was underwater for most of its life, it only hunted humans and other large animals above water or when they were underwater. It should be mentioned here that it attacked the neck as the only point on each of its victims in order to obtain blood. Victims of SCP-227-DE were usually hunted by it until they died by bleeding to death. It used its anomalous ability of sublimation and resublimation to confuse its victims. After event 227-DE/1, however, the nature of SCP-227-DE changed greatly to the opposite. It became calm, moral, intelligent, cooperative, and exhibited almost human-like behavioral traits. Nevertheless, it should be noted that despite this, the individual phases of the moon have a slight influence on the temper of SCP-227-DE. However, this influence is so slight that there is no effect worth mentioning on the nature of SCP-227-DE. It is unknown how exactly event 227-DE/1 could occur, but after interviewing SCP-227-DE, it was theorized that some sort of curse that had been on SCP-227-DE until the event was broken. For more information regarding this curse, see the document "Interrogation Protocol 227-DE" in the Addendum.
Furthermore, it has an additional anomalous effect, which only occurs when one of its victims survives the attack by SCP-227-DE. After about 24 to 144 hours, the victim transforms into a ghoul or vampire. Similar to his diet, the severity of this transformation seems to depend on the phase of the moon. More details can be found in the appendix "Transformation Table/227-DE". Transformed victims of SCP-227-DE inherit most of the abnormal abilities and are classified as SCP-227-DE-1 due to their relationship to SCP-227-DE. SCP-227-DE-1 instances appear to be under the full control of SCP-227-DE and obey it, though SCP-227-DE and SCP-227-DE-1 appear to share some sort of telepathic link, as it is unable to verbally issue commands or other instructions.
Due to its age and ability to transform victims into SCP-227-DE-1 instances, SCP-227-DE is believed to be the origin of most vampires and responsible for their sole creation. While it is unknown how it can transform its victims into SCP-227-DE-1 instances, this is the subject of an ongoing investigation.
Discovery: During a joint exercise dive by the MTF-DE7-𝔏 and the UFDF6 SCP-227-DE was accidentally discovered when it attacked the exercise divers. There it exhibited its anomalous sublimation and resublimation capabilities for the first time, causing the death of one MTF diver and severely wounding two others. With the assistance of the UFDF, SCP-227-DE could be tranquilized and confined with great difficulty. The severely wounded were given emergency care in one of the submarines. None succumbed to their wounds and SCP-227-DE was successfully contained for the first time in Site-DE7. After one day, however, it was decided that it would be re-contained in Site-DE6.
After half a day, the physician assistants in the emergency department of site-DE7 noticed that the severely wounded personnel started to change morphologically and behaviorally. At this point, the second anomalous ability of SCP-227-DE could be observed. They went wild and started lashing out, however, they suddenly showed superhuman strength and killed the three physician's assistants on the scene who were trying to fixate them. Due to the quick reaction of the RTF-DE7-ℑ, the two SCP-227-DE-1 instances that emerged were eliminated early on.
Addendum: The following is the interview protocol 227-DE