Thanks to TARDIS Wikia
Davros was originally the head of the Kaled Scientific Elite, on the planet Skaro, but became better known as the creator of the Daleks. During the Imperial-Renegade Dalek Civil War, he served as Emperor of the Imperial Dalek faction and later of the Dalek race as a whole, but his relationship with his creations was always tense. He was frequently hunted, maligned or otherwise denigrated by some portion of the overall Dalek population.
Despite the fact that he was not the unquestioned ruler of the Daleks, he was one of the Doctor's greatest enemies, rivalling the Master in intellect and madness. Because of his creations, he was responsible for trillions of deaths and war across the universe.
As a child, Davros claimed that only his mother believed in him. Others feared him and his determination and were right to do so. His stepfather, Colonel Nasgard (whom both believed to be his biological father), wanted him to become a soldier like his ancestors but Davros was determined to become a scientist. (Innocence)
During his childhood, he watched the propaganda television series Captain Croag and the Highland Rangers, as did Yarvell. (Guilt)
As a child, Davros often read the Book of Predictions, which was written in the extinct language of the Dals. Although the book was banned by the Council of Twelve, he kept it in his possession for decades. (Innocence, Guilt)
Shortly after his stepfather's death, Davros joined the Military Youth before joining the Military Corps in his final year of college.
In Nasgard's will, the family finances were held in trust under Davros' name and his wife and daughter were forbidden access to it until Davros was married. Due to her connections with senior members of the Kaled judiciary, Calcula was successful in her attempts to have the terms of the will overturned. Prior to this, she had attempted to set Davros up with the daughter of Councillor Matros, another member of the Council of Twelve who belonged to one of the most influential and wealthy Kaled families. (Purity)
Davros' first assignment in the Scientific Corps was in food processing. Consequently, he learned that the pills were made from not only waste vegetable matter but also the bodies of the dead. (Davros)
One month after the death of his mother, Davros was grievously wounded by a Thal bombardment of his laboratory in the Kaled Dome which cost him his eyes, taste buds, left arm and entire lower body. As a result, he was forced to spend the rest of his life confined to a mobile life support system.
After he was crippled, the Scientific Corps gave Davros a projectile poison injector to allow him to kill himself. He kept it but refused to use it. (Davros, Corruption)
Thirty seconds without his life support would have killed him. The life support system was controlled by a switch on the panel of buttons on his system. (Genesis of the Daleks) His chair acted like an iron lung and pacemaker in that monitored and maintained his body. (Davros)
He did not require nourishment due to his life support system, although he did occasionally eat. (Davros, Guilt)
After he assassinated the Supremo and the other members of the Council of Twelve, Davros became the de facto Kaled head of state as their deaths left him as the most senior surviving civilian in the Kaled Dome.
Davros began experimenting with organisms and teaching them to speak. In particular, he taught them to say his name. For his first experiment, he used a Thal brain, that of a spy named Baran, instead of a Kaled one. (Guilt)
CREATION OF THE DALEKS
However, intervention by the Time Lords began a chain of events. The Fourth Doctor was sent to Skaro at this time when Davros first demonstrated the Daleks to the Kaled Scientific Elite. Davros imprisoned the Doctor. He used a lie detector to force the Doctor to reveal the details of the Daleks' future defeats, so that he could learn from them and so his creations, the Daleks, could avoid them. (The Doctor later had this record destroyed.) Davros refused to listen to the Doctor when he begged him to instead make the Daleks peaceful creatures of good, rather than the evil exterminators they would become. (Genesis of the Daleks)
The extent to which the Time Lords' intervention changed history was unclear. However, prior to the known involvement of the Time Lords, Dalek history was quite different. In the pre-Time Lord history, Daleks were created by an entirely different person, Yarvelling, under circumstances that were only passingly similar, and by people whose physiology didn't match the humanoid Kaleds attendant to Davros. (Genesis of Evil)
"DEATH" AND REVIVAL
Davros' suspended body was eventually found in the underground remains of the crumbled bunker and he was revived. Davros opted to help the Daleks in their war against the Movellans. He devised a plan to destroy a Movellan ship. After this failed, he was captured by the Doctor and the escaped Dalek slaves, and imprisoned in a cryogenic freezer as "a block of ice". (Destiny of the Daleks)
War of the Daleks claims that Davros was moved, unbeknownst to him, from Skaro to a decoy planet called Antalin, as part of a plan by the Daleks to stop Skaro's destruction. Most of this is explained by the Dalek Prime, who might have been lying.
A NEW ENTERPRISE
Davros gained a foothold and claimed to be working on a way to combat famine. He held great interest in the stock market and planned on closing it down by broadcasting a pattern he discovered, the results completely disrupting the Galaxy and enabling Davros to gain a military foothold. However Davros began to be haunted by his past, particularly the time before his accident when he had betrayed a female Kaled scientist named Shan whom he perhaps had loved. The Doctor halted his plan but Davros escaped in a ship. The Doctor took control of the ship from the TAI control room and made it crash while Davros screamed Shan's name. (Davros)
EMPEROR OF THE IMPERIAL DALEK FACTION
En route to Skaro, the ship carrying Davros crashed on the planet Lethe. Davros was rescued. He set himself up as 'Professor Vaso', altering the perceptions of the humans on the colony so they would not recognise him as the 'Great Healer'. He attempted to create a new machine, a Juggernaut based on a Mechanoid design.
Lethe's atmosphere prevented the Supreme Dalek retrieving Davros directly, but its forces intercepted the Sixth Doctor's TARDIS, forcing him to serve as an agent of the Daleks and stop Davros' researches and manipulations. The Doctor discovered two of Davros' Necros Daleks had survived the crash, but were destroyed following Davros' final gambit on the colony and the Supreme Dalek's intervention. (The Juggernauts)
Following this event Davros was most likely retrieved by the Dalek Supreme's forces once more and returned to Skaro.
By suggestion of the Doctor, (Up Above the Gods) Davros hid himself on Spiridon, along with his empire of Daleks. The Daleks who had put him on trial before came to return him to Skaro, but his Daleks held them off. Davros detonated the planet, killing the Daleks. He woke highly injured, four days into the Dalek civil war, in a new casing as the Dalek Emperor. (Emperor of the Daleks!)
By the time of his attempt to recover the Hand of Omega from Earth in November 1963, Davros had proclaimed himself the Dalek Emperor. He was completely encased within an Imperial Dalek-like shell, though his head and upper body still appeared to be at least partially Kaled. He was nearly killed when his ship was destroyed by the Hand of Omega, but survived once again in an escape pod. (Remembrance of the Daleks)
AFTER THE HAND OF OMEGA
This is the second.
At some point while Emperor Davros developed mind-transfer technology and formed an alliance with Napoleon in the hope of changing history by altering the outcome of the Battle of Waterloo, planning to replace Napoleon's mind with that of a Dalek and use Napoleon's mind for the Dalek battle computers. The Sixth Doctor found Davros in 1815 and transferred minds with him. Davros' mind was transferred back but the Doctor revealed the deception to Napoleon, who deliberately lost the battle. (The Curse of Davros)
DURING THE LAST GREAT TIME WAR
FOLLOWING THE LAST GREAT TIME WAR
Davros had once again become a slave of the Daleks, who had placed him under guard within the Vault on the Crucible as part of a deal he made with the Supreme One. This arrangement required Davros to build a Reality bomb powered by the Crucible and the twenty-seven planets in the Medusa Cascade to destroy all of existence, leaving the Daleks the sole inhabitants of the universe. However, the Meta-Crisis Tenth Doctor and Donna intervened, destroying the new Daleks and leaving Davros on a burning Crucible. Before leaving in the TARDIS, the real Doctor offered to save Davros, but the creator of the Daleks refused, blaming the Doctor for what had happened and naming him "The Destroyer of Worlds". Davros ultimate fate was never confirmed. (Journey's End)
Davros also created an Imperial faction of Daleks to counter what he saw as a Renegade faction of Daleks, as well as the cybernetic Juggernauts by combining human components and DNA with the robotic Mechanoids. (The Juggernauts)
Brilliant and driven, he relentlessly experimented to find the final form of the Kaled people. Although he respected the Fourth Doctor as a fellow scientist, he refused to make the Daleks into less vicious creatures, which almost resulted in his death. His respect for the Doctor had faded completely by the time of the war in the Medusa Cascade and he took a sadistic pleasure in reminding the Doctor of how many people had died for him and even implied that he considered the Doctor to be a coward calling him "the man who keeps running". The final words Davros ever spoke were to insult the Doctor and he screamed "You are the destroyer of worlds!" (Corruption, Guilt, The Stolen Earth, Journey's End)
Davros was malevolent and sadistic; it was his ability to command and delegate that was most forceful and cold. While his conversation with the Doctor following his awakening (Destiny of the Daleks) suggests that he may have survived the extermination attempt through forethought, it seems to have made Davros even more bitter. This led him to making what would later be the Imperial Daleks. (Resurrection of the Daleks)
After his supposed death and rescue from the Last Great Time War, Davros arguably seemed less power-crazed and somewhat defeatist, perhaps due to having lost control over the Daleks yet again and being aware that once he was of no further use to them, they would exterminate him. He also seemed to have developed a dislike of pride and vanity: he admonished the Dalek Supreme for displaying pride, and distastefully noted "arrogance" in the Doctor's voice. Davros was also a hypocrite which was shown when he himself displayed pride when he refused the Doctor's offer to save him from the exploding Crucible, choosing death over capture. He was also a complete maniac, arguably even more than before and was consumed by an insane desire to completely destroy the entire universe. (The Stolen Earth / Journey's End)
Davros did possess a sense of humour, however rarely it was expressed. He coldly quipped that informing the beneficiaries of his Necros-produced protein that they would be eating their own relatives would have created "consumer resistance". (Revelation of the Daleks) He once remarked to the Doctor that "Your appearance is as inconstant as your intelligence", and when the Doctor reminded him that he had defeated him each time they had met, Davros laughed and replied "You flatter yourself!" (Remembrance of the Daleks) He later seemingly parodied his own hyperbolic tendencies when listing the Doctor's failures, ending with the matter-of-fact statement "oh, the end of the universe has come". (Journey's End)
Following his cryogenic imprisonment, Davros's face gained a yellowish, sagging appearance, probably caused by the effects of the time he spent in sub-zero conditions. (Resurrection of the Daleks)
Davros's chair had anti-gravity gravitors that enabled him to hover, possibly an upgrade. (Revelation of the Daleks)
On Necros, Bostock fired a gun which destroyed most of his right hand and with it his ability to operate independently. (Revelation of the Daleks) For a short time after, his hand was replaced with a claw (Emperor of the Daleks) and finally with a prosthetic substitute of futuristic design (The Juggernauts, The Stolen Earth, Journey's End). He was capable of projecting electric shocks from both his organic and mechanical hands and his eye, allowing him to ward off attackers and stun or even kill them. (Davros, Revelation of the Daleks, Journey's End)
By the time that Davros had risen to become the Emperor of the Imperial Dalek faction during the Imperial-Renegade Dalek Civil War, his life-support chariot no longer featured a button with which he could deactivate his life support, (The Curse of Davros) as it had when he had first met the Doctor on Skaro. (Genesis of the Daleks)
At some point during or after the Time War, Davros would dispense with his skull wires and throat microphone, possibly due to having gained access to more advanced medical equipment. However, he retained his head brace. (The Stolen Earth / Journey's End)
BEHIND THE SCENES
For Destiny of the Daleks, David Gooderson took over the role for the unavailable Wisher.
Subsequently, Terry Molloy, who first appeared in Davros' third story, Resurrection of the Daleks, has played the role on television and audio more times than any other actor, beginning in 1984. Rory Jennings played Davros as a child in an extended flashback sequence in the Big Finish Productions audio mini-series I, Davros, which examined Davros' life before creating the Daleks. Molloy has stated that Julian Bleach's performance has stayed true to the type of person that Davros seems to be.
In The Curse of Davros, Davros was played by Colin Baker as the Sixth Doctor switches bodies with Davros in an attempt to reform the Daleks.