The 'Shalka' Doctor was a possible 9th incarnation of the Doctor, whose existence was likely negated by the events of the Last Great Time War.
He had an appreciation for the finer things in life, and although he shared with his other incarnations an abhorrence of evil he possessed an intellectually superior attitude that frequently bordered on snobbery. Beginning his incarnation as a bon vivant, he demonstrated a fondness for singing, and had a repertoire of showtunes. However, the death of a companion saw him become far more world weary, melancholic and standoffish in his behaviour; though his fondness for singing remained, it was accompanied by what might be described as a drinking habit.
By the time he met Alison Cheney, he also known to demonstrate an abrasive attitude to working with the military, and demonstrated a strong negative reaction to being offered a firearm.
Early in this incarnation's life, he was travelling alone when he arrived on the human colony of Verdant during an invasion mounted by the Apan Hive. During these events, he met a conman pretending to be him and learnt that an acquaintance from his 5th incarnation had been cloned and replaced by the invaders. (IA #27)
Later, he would acquire a female travelling companion with whom he formed a deep and enduring relationship that conjecturely may have been similar to that shared with Rose Tyler by the 9th and 10th Doctors. Her death would have a profound effect on him — though little is known about her life or death, it may be conjectured that her demise tragically occurred at the Doctor's own hand. For reasons unexplained but likely as a direct result of this he started travelling with a TARDIS-bound android containing the consciousness of the Master.
During ths time, the Doctor took a shuttle cruise to Argolis for a vacation; it rained the entire time. On the return journey he kept the inflight magazine, which featured an article about the sudden appearance of a mysterious pyramid above one of the cities of a human colony world.
The duo eventually fetched up involuntarily in the Lancashire village of Lannet in the early 21st Century AD, apparantly at the silent behest of the Time Lords to investigate the Shalka invasion which had its beachhead there. A combination of resentment and reluctance led to his refusal to intervene until the death of a homeless woman raised his ire. To avoid capture by the Shalka, he tried to act the part of a detached alien observer but betrayed himself when he refused to allow them to kill Alison Cheney. After the Shalka were defeated the Master invited Alison to travel with the Doctor, an offer she accepted. (Scream of the Shalka)
Shortly afterwards, the TARDIS materialised in a cave on an unknown planet that had been the site of a long vanished blood cult whose practices had imprinted the stones with a form of psychic vampire awoken by accidental contact with the Master's mind. Though the Doctor was rescued by his android companion, he was forced to deactivate the Master in order to rescue Alison, which unintentionally led to heightened tensions between the three travellers. The Feast of the Stone
In an attempt to soothe matters over, the Doctor decided to fulfil his promise to take Alison to see the pyramids by taking her to witness the event mentioned in the magazine. The Master used to opportunity afforded by what turned out to be the beaching of a Time Lord trans-dimensional obervatory to attempt to escape his imprisonment: the ensuing tragedies resulted in the Doctor stripping his erstwhile friend of a body altogether and "trapping his mind in a box" for the forseeable future. (IA #28)