Mastermind is a whip-thin male NightWing scientist, with bloodshot eyes and small scars on his snout. As his name implies, he was the genius behind the NightWings' plan to overthrow the RainWings. He is the father of Starflight, his mate being Farsight, who had died a few years before the events in the first arc. He had claimed that Starflight was his son for six years, but couldn't prove it until he met him. He mentioned Starflight to look like him, and described their silver scaled wing patterns like an outward spray of water, as well as pointing out their jawline was 'genetically dominant'.
When Morrowseer and Starflight were on a hunt, Starflight remarks disgustedly that he would not have developed the correct antibodies to protect against the dangerous effects of eating dead NightWing food. Morrowseer then comments he now knows who the dragonet's father is, based on Starflight's so called 'speaking style'. Morrowseer takes him to visit Mastermind. They meet Fatespeaker on the way to the laboratories inside of the fortress.
Mastermind is in the middle of a 'crisis' when they arrive, the crisis being constructing venom proof armor, and tells them to leave because Princess Greatness threatened to shut his research down. Morrowseer informs Mastermind that Starflight is his son, at which point he calms down and first examines Starflight, overjoyed to have found his son. He then begins talking about how certain traits they share (such as their jawline and the water spray silver-scale pattern on their wings) were genetically dominant, then shows the two dragonets some of the experiments he is working on, including desalinization and vulcanology. Starflight is awed by it all, and is wanting to work with his father.
Mastermind then shows them his current project- RainWing venom and its capabilities. In order to study the venom, seventeen RainWings, three of which did not survive, were brought from their homes to the Night Kingdom against their will, and were then imprisoned so that Mastermind could safely conduct his experiments on them. He was working on Orchid at the time. He wanted to learn more about RainWing venom, such as what materials it affects and what it doesn't. Mastermind learned that it only affect organic matter, and will quickly kill anything if the venom gets into either the eyes or the bloodstream. He then began the construction of armor to resist the venom, but could not finish it due to being unable to find a suitable material as the eyepiece. However, he was so caught up in his research it never occurred to him that he was torturing the captive RainWings. This caused Starflight to decide that his father was sociopathic. He wanted nothing to do with Mastermind and his venom experiments and tried to avoid him.
Mastermind was also secretly working on lava-heated armor that would enable Queen Battlewinner to leave her pool of lava without freezing to death. This way, she would be able to lead the attack on the rainforest. Starflight saw it, but did not assume who it was for, and why. However, the armor never achieved completion before the eruption of the volcano, which destroyed everything on the NightWing island. The armor was presumably destroyed during the eruption.
Before the volcano exploded, rendering the Night Kingdom uninhabitable, Mastermind was among the evacuating dragons. He was bringing with him a bundle of scrolls, much like Starflight had tried to do so in the underground cave. He voiced his worries about the RainWings hating him for what he has done to their tribe to Starflight and Tsunami. Starflight sensed his father wanted to hear an assuring lie. Instead, he told his father to apologize to the Queen and take whatever punishment she gives him, and Mastermind escaped through the rainforest tunnel with the rest of the NightWings. His labs and research were all destroyed in the eruption; only the scrolls that he brought with him were saved.
Two RainWings brought Mastermind to Queen Glory. She ordered him to be tied up until she could decide what to do with him. As of the epilogue, he was awaiting to stand trial for his crimes against the RainWings.
Mastermind yelled at Strongwings when he was his assistant, telling him to never come back again because Strongwings ruined Mastermind's lab somehow by knocking over a bottle of "uh, something" into a vat of "something else".
When they were talking about prisons, it was brought up that the RainWings don't have such things. Mastermind was mentioned to have been submerged in quicksand, since the RainWings didn't have prison cells and don't want to kill him. The RainWings had to haul him out every few hours so he doesn't sink.
When Darkstalker created a prison, he mentioned that Glory could put Mastermind in there instead of leaving him in quicksand.
Mastermind is highly intelligent, as he is a NightWing scientist. He is passionately devoted to science. He seems to care greatly about Starflight, and has a tendency to use complex vocabulary, just like Starflight. He gets nervous in tough situations, such as when Battlewinner left the pool of lava before her armor was complete, ultimately leading to her death. Mastermind was loyal to his tribe, and was willing to follow the queen's orders. However, Mastermind did not have any intentions to torture the RainWings nor the tribe. He only intended to create defense to RainWing venom and expand dragon knowledge for the purpose of science, as well as following Queen Battlewinner's orders. He seemed to considered RainWings to be an inferior tribe which is why he showed no remorse in their oppression.
"No, no! I must not be interrupted! This experiment is at a critical juncture! And Greatness says I might be shut down at any moment! Everyone please leave!" - To Morrowseer, Starflight and Fatespeaker.
"My son?" - To Morrowseer.
"Three moons, what a handsome dragonet. He does look like me; I knew he would. As I suspected, his jawline is genetically dominant. Ah, and yes, see the way the star scales on our wings spray outward, like a splash of water. whereas Morrowseer's, for instance, curl inward, more like a snail shell. All theories at this point, of course." - To Morrowseer about Starflight.
"But I have a son! I, of all dragons! Let's see Strongwings laugh now! Just wait until everyone sees my handsome offspring. So strong and healthy! You can be the assistant I've been looking for. What are you interested in, son?"
"Come, come. I'll show you what else I'm working on."
"Here is where I do all my vulcanology."
“YOU’VE RUINED IT! THE WHOLE THING! OUR ENTIRE TRIBE COULD BE WIPED OUT BECAUSE OF YOUR STUPIDITY!”
"DON'T COME BACK OR I'LL DISSECT YOU ALIVE!" - to Strongwings after he messed something up. Again.
"Should I be concerned?" -While evacuating the Night Kingdom
- Mastermind's name is very accurate due to the fact that he almost succeeded completing Queen Battlewinner's plan of taking over the rain forest.
- He almost succeeded in making RainWing venom proof armor, as well as helping Queen Battlewinner have a container allowing her to walk without freezing to death.
- Mastermind is the first dragon in the Wings of Fire series performing scientific experiments.