Cloister Bell

The Cloister Bell was an alarm bell located in the Cloister Room inside TARDISes. The Cloister Bell was used in the most serious of emergencies, which saw either the TARDIS or its inhabitants in danger.

Its distinctive, sonorous, ringing sound resembled that of a large church bell. It could be answered by anyone inside the TARDIS. The Fourth Doctor told Adric that if he needed him, Adric could sound the Cloister Bell, indicating it could be manually activated. (TV: Logopolis)

It had the physical appearance of a large, golden bell. (COMIC: Four Dimensions)

Cloister Bells were located in the Cloisters of Gallifrey and could be heard all over the planet when sounding. (TV: Hell Bent)

Instances of the Cloister Bell ringing
The TARDIS mistakenly believed it was being attacked by the Pus Creatures of Rakos as it materialised in Magnus Greel's bunker. While the Fourth Doctor slept, Romana II apologised for the interruption that it had caused. (PROSE: Under Reykjavik) As a harbinger of the Fourth Doctor's impending regeneration at the hands of and as a warning of his actions nearly destroying the universe, the Cloister Bell sounded. (TV: Logopolis) During the Fifth Doctor's very early life, the Cloister Bell rang as the TARDIS was travelling back in time to Event One. (TV: Castrovalva). Later, when an established time corridor, through which the TARDIS was travelling, began collapsing, the Cloister Bell also rang. (AUDIO: The Mutant Phase) It sounded when the TARDIS was trapped in a Dalek time corridor, and under imminent threat of destruction. (TV: Resurrection of the Daleks) As a harbinger of the Seventh Doctor's impending encounter with the Timewyrm and when the Doctor started to time ram her, the Cloister Bell sounded. (PROSE: Timewyrm: Genesys) Later in the same adventure, the Cloister Bell rang as the Doctor took the TARDIS into his own mind. (PROSE: Timewyrm: Revelation) Later in the Seventh Doctor's travels, the Cloister Bell indicated the TARDIS' distress after a link to the Eye of Harmony was damaged. (PROSE: Cat's Cradle: Witch Mark) It was also heard when the Seventh Doctor was being called by the Sirens of Time. (AUDIO: The Sirens of Time) The Cloister Bell rang out near the end of the Master's scheme to capture the first seven incarnations of the Doctor, when it was revealed that they were never freed. (GAME: Destiny of the Doctors) Just prior to the destruction of the TARDIS by the Selachians in an alternate timeline created by Elizabeth Klein, the Cloister Bell sounded. (AUDIO: The Architects of History) During the beginning of the Eighth Doctor's life, the Master opened the Eye of Harmony in an attempt to take the Doctor's remaining regenerations. The Cloister Bell rang to signal the impending danger. (TV: Doctor Who) The Cloister Bell was also heard through the Eighth Doctor's regenerations, including his travels with Lucie Miller. When Vortisaurs attacked the TARDIS whilst in flight in the Vortex, it was heard. (AUDIO: No More Lies)

During his travels with Samantha Jones, the Cloister Bell rang when the unstable alternative timeline created by the Tractites began collapsing, taking the multiverse with it. (PROSE: Genocide)

It could also be heard by the Eighth Doctor and crew during Ed Hill's attempt at disrupting the Eye of Harmony. (PROSE: Revolution Man)

It was heard by the Eighth Doctor when the TARDIS was hit by the temporal wave of the Dalek's Time Destructor during the Last Great Time War. (PROSE: Natural Regression)

During the Last Great Time War, the War Doctor voluntarily surrendered to a Dalek fleet near the Tantalus Eye. The bell rang and his companion Cinder construed it as the TARDIS herself disapproving the Doctor's plan. (PROSE: Engines of War)

As the Tenth Doctor began to fly the TARDIS erratically and at ever-increasing speed, the TARDIS signalled danger by ringing the Cloister Bell. (TV: Children in Need Special) Also, when cannibalised the Tenth Doctor's TARDIS, turning it into a paradox machine, the bell sounded as well. (TV: The Sound of Drums)

When the Sonic Screwdriver detects a Black hole the Cloister Bell is heard. (GAME: Sonic De-Cloaker)

When the Tenth Doctor and Fifth Doctor's TARDISes crashed and merged together, the TARDIS rang the Cloister Bell. (TV: Time Crash) The TARDIS also used it as a warning of the impending "end of the universe". (TV: Turn Left)

During his travels alone and following the destruction of Bowie Base One, the Tenth Doctor heard the Cloister Bell inside the TARDIS as his own demise loomed, this led to the projection of Ood Sigma as a warning of his inevitable fate (TV: The Waters of Mars) and was also heard when the TARDIS chicks appeared in the TARDIS. (COMIC: Terror in the TARDIS)

During the Eleventh Doctor's life, the Cloister Bell sounded as the TARDIS' engines were in danger of phasing out of existence after his regeneration energy had destroyed the console room. (TV: The Eleventh Hour)

In his later life, the Eleventh Doctor heard the Cloister Bell when the Entity was interfering with the TARDIS' systems. (GAME: TARDIS) They also sounded when the Siren teleported the TARDIS aboard her home ship. (TV: The Curse of the Black Spot)

When the TARDIS was taken over by House, the TARDIS showed its distress by using the Bell. (TV: The Doctor's Wife) The Eleventh Doctor heard the Cloister Bell when he opened the door to his "greatest fear", (TV: The God Complex) which turned out to be the cracks in the universe caused by the destruction of the TARDIS. (TV: The Time of the Doctor)

When the TARDIS got caught up by the time storm created by an Eternity Clock, it was also heard. (GAME: The Eternity Clock) The Bell also rang when the Eleventh Doctor was trapped in a pocket universe (TV: Hide) and when the Van Baalen Bros.' magnetic hobble-field locked onto and damaged the TARDIS. (TV: Journey to the Centre of the TARDIS)

It was heard as the Great Intelligence entered the Doctor's tomb and again when the Great Intelligence entered the Doctor's time stream. (TV: The Name of the Doctor)

During the beginning of his life, the Twelfth Doctor fainted after regenerating, causing the Cloister Bell to ring. (TV: Deep Breath) Later in his life, as the Doctor was unconscious in the TARDIS while it was seemingly TARDIS under attack, the Bell again sounded. Clara recognised the sound as a signal of danger. (TV: Listen)

The Cloister Bell sounded when the TARDIS, in a weakened state, fell into the path of an oncoming train.. (TV: Flatline)

Whilst in a dream-like reality, Clara threw a TARDIS key into an active volcano. As the key was melting, the TARDIS Cloister Bell was heard. (TV: Dark Water)

The Cloister Bell rang right before the Eleventh Doctor, Alice Obiefune, John Jones, and ARC crashed and were separated in four dimensions. (COMIC: Four Dimensions)

The Cloister Bell rang again when the TARDIS arrived on the Drum (TV: Under the Lake) and again when the TARDIS time-traveled to thirty minutes earlier in 1980 then it had previously been. (TV: Before the Flood) It rang one more time when Clara Oswald was lost in space. (TV: The Girl Who Died)

The Gallifrey Cloister Bells rang upon the Twelfth Doctor's return to Gallifrey which also activated the Cloister Wraith. (TV: Hell Bent)

Behind the scenes

 * The sound of the Cloister Bell was made by hitting a gong in a pool of water.
 * The Bell was not heard on-screen until towards the end of the Fourth Doctor's life and was not heard during other incidents of danger during the following episodes:
 * The looped death of the TARDIS (TV: The Pandorica Opens/The Big Bang) and the activation of the HADS when the TARDIS felt it was under attack. (TV: Cold War)