Special Containment Procedures:
For permanent containment and prevention of SCP-6505, the Foundation would have to ward off every graveyard and churchyard within the British Isles. Due to the impracticability of proper containment, the specific requirements for SCP-6505's activation and the negligible, unremarkable and beneficial nature of SCP-6505-1, it has been determined that special containment procedures are not required.
Research of SCP-6505 is currently being conducted at Site-24, performed by the Department of History and the Department of Mythology and Folklore. Any investigations or documentation of SCP-6505 by non-Foundation researchers must be discredited.
Description:

An instance of SCP-6505-1 interacting with an individual during an SCP-6505 event.
SCP-6505 is an anomalous phenomenon that occurs within churchyards and graveyards in the British Isles. According to historical and statistical records, SCP-6505 events are more common in graveyards situated in rural or low-population-density areas. An SCP-6505 event is activated when a human visits a grave within the graveyard, known as the 'visitor'. The visitor has to have had a relationship with the deceased individual/s buried in the grave and be undergoing some form of personal conflict regarding the deceased for SCP-6505 to activate. Observation has discovered that SCP-6505 can be activated by multiple visitors (to date, a maximum of 3) if conditions are satisfied, although SCP-6505 is more likely to occur with a single visitor. Upon activation of an SCP-6505 event, a single SCP-6505-1 will manifest within the ground of the graveyard and engage with the visitor/s.
SCP-6505-1 are adult dogs, typically black in colouration, although some white or patched instances have been recorded (~11%). SCP-6505-1's breed varies, although they always manifest as a dog of a particularly large breed. All instances of SCP-6505-1 are very engaging, friendly and playful. Testing has proven only a single instance of SCP-6505-1 can manifest within the area during an SCP-6505 event, although if multiple SCP-6505 events occur in separate locations, each one will manifest its own instance of SCP-6505-1. SCP-6505-1 is unlikely to manifest if the area is heavily crowded, such as during funerals or religious services, although some instances have been observed doing so whilst maintaining distance.
When the visitor/s interacts with SCP-6505-1 for approximately 5 to 15 minutes, the visitor/s will recall forgotten or doubted memories and information relating to themselves and the deceased individual/s. These memories, whilst not always positive, have some inherent benefit, either psychologically or practically and will help them resolve their conflict. Upon this realisation, SCP-6505-1 will then disengage with the visitor/s and demanifest when no longer observed. The visitor/s can continue to interact with SCP-6505-1 after the realisation, although SCP-6505-1 will become agitated and disinterested.
Analysis by the Department of Applied Thaumaturgy has discovered that during an SCP-6505 event, the surrounding area's Akiva Radiation levels increase slightly, with SCP-6505-1 showing the greatest level of thaumactivity. These levels of activity are consistent with those found surrounding a Spectral Entity, suggesting SCP-6505-1 instances may be spectral anomalies. However, this conflicts with the fact that SCP-6505-1 instances leave physical evidence such as hair and saliva1. This implies that whilst they aren't spectral in nature, SCP-6505-1 may possess astral or chthonic capabilities. Research into SCP-6505-1 capabilities is ongoing.
Addendum 6505.1: History
Research by the Department of Mythology and Folkloristics and the Department of History have managed to recover numerous documentation of SCP-6505-1 instances, mostly from the 19th and 20th century. However, trace details of the event have been found as far back as the 7th century, predating Christianisation in the British Isles. It has been noted that SCP-6505-1 shares many characteristics with the Church Grim, a guardian spirit found in British folklore that oversees the welfare of churchyards. SCP-6505-1 also shares several traits with other canine entities found in British folklore, such as their black fur, large size and connection to death. Below is an extract from British historian and folklorist Horace Greenblatt's Terrors, Superstitions and Folklore (1868), which details these parallels:

A depiction of an SCP-6505-1 instance.
Black Dog Motif
Across all human cultures, all sorts of animals have acted as symbols, warnings, guardians and beasts. The hound, our loyal friend and companion, is one such animal, with almost all known mythologies recognising them in some way. Their portrayals vary, with some cultures associating them with faithfulness and protection. Others, believe them to be figures of violence and savagery. Although, one attribute remains fairly consistent within the folk-product; their role in death. Since the Neolithic, canines have been closely associated with the hereafter. Such an association is at its most common here, in the United Kingdom (see Lord Blackwood's 18th edition, Monsters of the Developing World). What possible reason could there be for such a large congregation of spectres? It is my conjecture that they result from our desire for protection and a practice, long forgotten.
In the times before civilisation, we have used hounds to act as our protectors. This protection extended beyond our mortal realm. Many folktales depict the hound with the capabilities of perceiving threats we can not. Beings invisible to our own senses, such as phantoms, spirits, boggarts and fairies, could be seen by hounds and feared them as a result. Such a defence would have been wanted to continue into the next life, the hereafter. To achieve this, when death claimed our companions, we would bury them alongside us in the mounds and flat graves, in the hopes they'd continue their defence in the hereafter. This practice, now considered barbarous, was once common and continued well into the formation of Christianity within the United Kingdom. Some of our oldest churches and sanctuaries have been shown to have a hound buried underneath their foundation. All with the hopes it would act as the guardian against the Devil and sacrilegious acts. We have even christened them with the title 'faire chlaidh'. In the Queen's English, we would call them the 'graveyard watchers', but the traditional name of 'church grim' is more familiar in the North.
Addendum 6505.2: Analysis
To test the connection between SCP-6505 and the role of canines in foundation sacrifices2, The Department of History and Department of Applied Thaumaturgy performed archaeological excavations of several chapels and churches with confirmed sacrifices. Upon excavation, the remains were fitted with Zohar counters and surveillance equipment was set up in the area with the intention of recording an SCP-6505 event and detecting the activation of any thaumaturgical programs3.
On 09/05/1999, an SCP-6505 event was activated in the St Illtyd's Church's4 graveyard in Bro Morgannwg, Wales. The activator, Cadi Iolo, was visiting her father's grave at the time. Below is a transcript of the footage of SCP-6505:
- Begin Log -
(Cadi Iolo approaches the grave of her father, slowing down briefly to read some of the other gravestones on the way.)
(Iolo remains standing in front of the grave for a few seconds, before kicking it hard. She proceeds to kick the grave six more times before stopping, nursing her foot.)
(A few seconds later, Iolo groans loudly, which disturbs some nearby pigeons. She then begins to cry angrily.)
Iolo: Oh, for fuck sake. Why did you have to do this dad?
(Iolo sits in front of the grave. She removes the ring from her left hand and turns it in her hand. The Zohar counter detects an increase in thaumactivity within the remains of the foundation sacrifice nearby. SCP-6505-1 manifests 10 metres from Iolo, in the form of the Hovawart breed.)
Iolo: It's too much. It's - the whole thing - and Bobby - and Ofsted coming - it's just - why did you have to die right now? It's - you're so selfish!
(SCP-6505-1 approaches Iolo, and nudges her with its nose.)
Iolo: Oh for fuc - Oh god! What! Oh - oh, hello.
(SCP-6505-1 attempts to engage with Iolo, tilting it's head and rubbing it's nose against Iolo's knees.)
Iolo: Yes. yes, hello. You - you're a big boy. Very big.
(Iolo begins to paw and scratch SCP-6505-1 which roll onto it's back and paws the sky.)
Iolo: Where's your owner? They'll be looking for - no - no collar? Hmmm?
(Iolo looks around. SCP-6505-1 continues to roll lazily on the ground.)
Iolo: Oh, there's the vicar's car.
(Iolo returns to petting SCP-6505-1. SCP-6505-1 yawns lightly and sniffs around the gravestone.)
Iolo: (sniggers) If you're trying to sniff out dad, good luck. We only just buried him.
(SCP-6505-1 sits in front of the grave. After a few seconds, Iolo begins to sing a tune under her breath, later identified as Chwarae'N Troi'N Chwerw by Caryl Parry Jones.)
Iolo: Mae'r gwin yn troi'n sur. Da da da daaa da. Something something troi'n sur.
(Iolo looks down at the ring for a few seconds, then look at the church. SCP-6505-1 approaches her and wags it's tail.)
Iolo: Maybe. Bobby won't mind. And - and dad's here. It's old but - but he's here.
(Iolo slowly gets up and returns the ring to her left ring finger. As she makes her way to her car, SCP-6505-1 walks off towards the forest. the remains' thaumactivity decreases and SCP-6505-1 demanifests. SCP-6505 ends. Iolo turns quickly and looks around.)
Iolo: Oh, where's he gone?
(Iolo looks around for a few seconds before pulling out her keys and phone. She then dials a number.)
Iolo: (speaks to phone) Bobby? Yeah, yeah, I know - I know. I - I was visiting dad. Yeah - I just - I wanted to be upset. Listen - do you mind if we had the service - in Illtyd. So - so we could be near dad?
- End Log -
The breed of the SCP-6505-1 instance that manifested during SCP-6505 didn't match the breed used in the church's foundation sacrifice, which was a Belgian Sheepdog5. During SCP-6505, the remains of the foundation sacrifice thaumactivity increased and remained at a steady rate of 63.4 ⊕ until the completion of SCP-6505. Whilst the Zohar counter couldn't determine the thaumaturgic programs that were activated during SCP-6505, further data from later instances did measure a similar rate of thaumactivity (~0.56 ⊕). Research into the connection between SCP-6505 and foundation sacrifices remains ongoing.
Five months after the analysis, Cadi Iolo married her partner, Robert Smyth in the church, surrounded by their respected families. No SCP-6505 event was detected.