Pre Crisis
In his first appearence, it was revealed that he had captured Hal Jordan and replaced him in the Justice League using a device he invented. Once his identity is exposed, he attacks the Justice League and captures them.
The Justice League are beaten by duplicates who are apparently more powerfull than them ..
After he is defeated and the device destroyed, Doctor Destiny descovers that he can now transmit dreams directly into the mind of the Justice League and the materialize those dreams using the Materioptikon he built in the dream-world. He builts adversaries for Batman,Superman,Hawkman,Wonder Woman and the Atom aswell as objects which interfere with their abilities, allowing them to momentarily gain an upper hand on the league.
Using his Materioptikon, Doctor Destiny transforms the Justice League members into villains.
He also apparently put the villains into a dream-state and in case anything would go wrong, they would wake up and attack the Justice League.
Using the device, Doctor Destiny also made the Atom dream he was actually at the meeting with the rest of the Justice League.
The Justice League each dream of certain tragedies ..
All of this happening due to Doctor Destiny. It is also revealed that his ability to dream has been removed by a psychiatrist sent by the Justice League which badly damaged his health. So he reconstructed an improved Materioptikon, fashioned it into a ruby clasp and tried to destroy the Justice League.
He imprisons his psychiatrist and makes everybody think it’s actually him. Then also tests his machine on guy he eventually is betrayed by and kills.
Materializes secret dream-fears to confront the Justice League.
After being compelled to say the truth with the lasso, he reveals that he had built five machines of which Justice League had already destroyed 2, in order to end all sane life.
He apparently made contact with the dream-continuum due to meditation. He also says that his mind is very powerfull due to the exposure to his Materioptikon and that he somehow tapped into a cosmic energy source with which he can now create reality in the dream-world.
Using Sandman(Garrett Sanford)’s equipement he captured people and used their dreams against the Justice League. Among the projections he used is also a projection of Amazo, Dr Light and Tornado Tyrant. Zatanna transports herself, along with the rest of the Justice League in the dream-world where they fight Doctor Destiny but are defeated and imprisoned.
Post-Crisis
It is revealed that it was actually his mother who gave him the ruby and that the ruby is actually Sandman (Morpheus)’s in which the aforementioned included a part of his power.
Doctor Destiny remembers events that have taken place (Pre-Crisis) .. „I did…foolish things.Things to gravity.To identity.I traded their faces with their enemies, I pretended I was of their number ..”
He explains the Ruby’s power and also reveals that the machines he built were powered by the ruby. „People think dreams aren’t real because they aren’t made of matter, of particles. Dreams are real. But they are made of viewpoints, of images, of memories and puns and lost hopes .. The ruby seems to turn them into matter. It forces them to translate themselves into forms we can recognize in this world. It also controls dreams in their raw state. Your dreams. Anybody’s dreams.” It’s also revealed that he did numerous changes to the ruby which most likely is the reason Morpheus is struck unconscious once he holds the ruby.
He makes them love him and it’s also revealed that „…nightmares,sleeplessness and insanity reported earlier on local news is shaping to be a planet-wide phenomenon.”
Confession time ..
Decides to give them back their minds for a short while. „Why are you doing this stuff to us ? You’re going to kill us !”
„Why ? Because I can.”
Brings out the beast in them ..
Sandman, realizing they will fight, goes into the dream-world where Doctor Destiny follows him. There, he starts destroying the realm and the people are affected by what he’s doing, even Destiny “Find himself hesitant to turn to the next page in his book”.He apparently has the upper hand until he destroys the ruby and the power returns to Sandman, who choses to spare him despite what he’s done.
It is revealed that eventough Morpheus (Sandman) reclaimed his stone, it left residual energy which now Doctor Destiny uses. He apparently forced the Atom to have the same dream every night until he created a whole universe where the Justice League is held captive and if he kills the Atom, they will be stranded there and that Universe will phase into existence with the current one.
Batman describes that Universe ..
Somebody has been reaching into the Justice League’s mind and twisted their perception of reality and all around the world, people have been reciving superpowers.
The Justice League deduce that it’s the work of Doctor Destiny, „Master of the Dream Reality”.
It seems that Doctor Destiny wanted to be discovered so he planted subonscious seeds into the minds of the Justice League to ensure that they would fiind him.
