Davros

Psychotic genius and creator of the Daleks, Davros gained favour with a race doomed by centuries of war, the Kaled, and used mutated genetic material to produce a hideous creature, devoid of all emotion apart from evil, promising the Kaled that this was the key to the survival of their race.

Despite doubts and insecurity, the Kaled went along with his plan but were horrified to discover that the mutated creature would need a mechanical encasement in order to survive. The Kaled realized too late that Davros' plan was to create a virtually indestructible, unstoppable race of pure evil, and their civilization was eventually destroyed when the Doctor's compassion prevented him from destroying the Daleks at their inception.

Early Life
According to various sources, Davros was a Kaled scientist (and/or a doctor) who was injured (severely) in a Thal attack at some point early in the Thal - Kaled war.

Encounters with the Doctor
Davros' first encounter with the Fourth Doctor was on the planet Skaro when Davros introduced the Mark III Travel Machine to the scientific elite of Kaleds. The Mark III Travel Machine was what would later become a Dalek. (DW: Genesis of the Daleks)

Davros would next encounter the Doctor again during the Doctor's fourth incarnation and still on the planet Skaro. During this encounter he was captured by a group of humans who had been used as slaves by the Dalek force which had returned to Skaro (DW: Destiny of the Daleks).

Following this encounter Davros was kept in stasis until he was recovered and revived by the order of the Dalek Supreme for assistance during the Dalek - Movellan war. (DW: Resurrection of the Daleks)

Davros subsequently escaped the Dalek's grasp and set himself up as the Great Healer on Nekros, where he lured the Sixth Doctor, to Nekros. Davros was captured by Renegade Daleks to be taken and put on trial by the leader of the Renegade Daleks. (DW: Revelation of the Daleks, Remembrance of the Daleks)

Personality
Davros had a sound mind early in his life, and even into his later life had a brilliant mind.

Early Personality (post Thal attack)
Davros was a brilliant and driven scientist, relentlessly experimenting to find the final form of the Kaled people. Davros was a cool and sadistic person, it was his ability to command and delegate that was most forceful and cold.

Personality following attempted Extermination
Davros' attempted assination by his own creators appears to be the instigator in his decent into madness. While his conversation with the Doctor following his awakening suggests that he may have survived the extermination attempt through forethought, it does still seem to have made Davros more bitter than he had originally been.

Personality following stasis by humans
Following his imprsonment in stasis Davros suffered in a conscious waking state through however many hundreds of years of prison. It had made Davros much more bitter and cold towards humans despite their involvcement in the Dalek's campaign against the Movellans.

Personality in later life
Davros only continues to decend further into madness until by the end of one part of his life he is teetering on the edge of sainity when he encounters the Doctor on the Earth that he had taken over with a virus. Terror Firma

Physical Appearance
Davros was originally sitting upright in a movement and life support chair. With a central blue eye in the centre of his forehead it allowed him some semblance of sight. He only had one hand which he used to opperate various controls on his chair; which could perform various functions from controlling doors, mark III travel machines, to his own life support system.

Following his operation on Nekros he lost much of his hand and thus his independant operability.

By his attempt to recover the Hand of Omega from 1963 Earth he had lost much of his Skarosian body and was completely encased within an Imperial Daleks like shell, though his head and upper body appeared to still be at least slightly still a physical Skarosian.

Creations
Most notable of Davros's creations is the Mark III travel machine, which then became known as a Dalek.

Davros also experimented with other Dalek forms, such as a Dalek able to walk over rough terrain known as a Spider Dalek. (War of the Daleks).

Davros also created an Imperial faction of Daleks to counter what he saw as a Renegade faction of Daleks. Included within these Imperial faction was a Special Weapons Dalek, consisting of a large turret able to destroy many targets at once.

Davros's place in Dalek Continuity
Davros is the creator of the Daleks, this much is certain. However much of Davros's other continuity and his place in the Dalek time line is complicated.

Portions of the complication arise from varrying points of view and the affects of temporal manipulation upon the time line, in particular by the Doctor and his actions during the Dalek's creation on Skaro.

Appearances
Genesis of the Daleks, Destiny of the Daleks, Resurrection of the Daleks, Revelation of the Daleks, BF: Davros, The Juggernauts, Remembrance of the Daleks, Terror Firma, War of the Daleks