Temporal meta-collision

Temporal meta-collision was a term used by the Tenth Doctor to describe contact between multiple incarnations of the Doctor. (WC: Doctors Assemble!)

The Master
When the Master offered to assist the Cult of the Heretic in their plans to remake the universe, they agreed to the offer only if he would kill one of his past selves to prove his loyalty to their cause, as the Anomaly Cage would protect the Master from the resulting paradox. As a result, the Master attempted to ambush his past self during his assault on Tersurus (allegedly planning to just leave his other self in a near-death state that he remembered being in at that time of his life anyway), but the Cult deliberately sabotaged this attack so that they could create a more potent paradox by transferring the younger Master into the body of his future self and then kill the older Master in his past incarnation. The two Masters were able to escape the Cult with their immediate memories scrambled, but their travels in the wrong bodies nearly destroyed the universe due to the paradox, with whole segments of history being erased - including meetings with the Fifth and Sixth Doctor s - until the Seventh Doctor confronted both Masters at once and helped them realise what had happened. The Masters returned to their own bodies and attempted to leave the Doctor to die so that they could hijack the Cult's plan to remake the universe, but the Doctor was able to follow them and restore reality as it was, apart from sending the Masters back to their points of origin with no recollection of their interactions with the Cult. (AUDIO: And You Will Obey Me, Vampire of the Mind, The Two Masters)

, the nineteenth incarnation of the Master, (PROSE: Girl Power!) travelled through her time stream to recruit her, Tremas,  Bruce and , forming a band to compete on Battle of the Bands Beyond the Stars. The group planned to use the popularity of the program to hypnotise the audiences across the galaxy. According to Missy, the five spent "decades" preparing for the performance. (COMIC: The Five Masters) The group went on before the Twelfth Doctor and Clara Oswald due to a shift in the program's schedule, and the five revealed themselves to the pair. (COMIC: The Abominable Showmen) Missy expected the Doctor to attempt to stop the five of them, or to at least esquire on their plans, but the Doctor refused to intervene or question their scheme. After much prying, the Doctor correctly predicted the group's plan, but still refused to intervene as they started their song. As she prepared to hypnotise her audience, her previous incarnations began to fight with her over her device, as each wanted to control the universe without the others. During the fight, viewers began to turn off their sets and the group were soon all disqualified and were thus blown up, although neither Clara nor the Doctor believed that they had truly been killed. (COMIC: The Five Masters)

When the Eleven formed an alliance with the Ravenous, the Master became aware of it in three different incarnations; the Master in Bruce's body met the Eighth Doctor while working with the Gallifreyan scientist Artron to try and gain new life energy in Gallifrey's distant past, the War Master responded to a call for help sent by Liv Chenka from a Time Lord waystation the Master had claimed as a base, and Missy later responded to another call for help from her predecessors and abducted Helen Sinclair to pursue another lead to Artron's current location. Not wanting the Ravenous to destroy the universe, the three Masters collaborated to undo the Eleven's plan to grant all life in the universe the ability to regenerate via the Crucible of Souls while the Doctor helped Artron realise how he could stop the threat posed by the Ravenous. When the Eleven attempted to propose an alliance between himself and the Masters against the Doctor, the Masters shot the Eleven and abandoned him with a vortex manipulator as he began to regenerate. The alliance between the Masters concluded with the revelation that the War Master had been assigned by the Time Lords to retrieve Artron's Matrix print from the Eleven so that it could be used to give Time Lords a new regeneration cycle, only taking a detour to restore a dead version of themselves to life (a future version of the Master in Bruce) with a new cycle of standard regenerations as part of the War Master's deal with the High Council. (AUDIO: Day of the Master)

Missy later inadvertently came into contact with her immediate predecessor aboard a Mondasian colony ship while in the company of the Twelfth Doctor. (TV: World Enough and Time) Though they initially joined forces, Missy ultimately elected to side with the Doctor against the Cybermen, resulting in her being killed without the opportunity to regenerate by her predecessor, though not before she mortally wounded him and thus initiated his regeneration. (TV: The Doctor Falls)

Others
Eleven of Drax's thirteen incarnations teamed up in order to con the Fourth Doctor into stealing a Blinovitch Limitation Effect limiter, which was what allowed them to cooperate on this scheme in the first place. It would appear that the Draxes used this technology to complete various other schemes in their lives, the different Draxes working together to complete complex plans that would have been harder for any individual incarnation to pull off. (AUDIO: The Trouble with Drax)