Sean Miller, also known as Astro, is a U.S. Recon Marine.
Through unknown circumstances, Sean Miller joined the United States Marine Corps, where he gained the call-sign Astro due to his love of science-fiction stories.
In August 2005, Astro was among Shane Schofield's ten-person team sent to HALO jump with other specialised units onto the deck of the USS Nimitz, which had apparently been forced by a tsunami to dock at the Hell Island base and was now no longer to communications.
As they moved to investigate the ship's main hanger, Sanchez attempted to convince Astro that the rumours of Schofield having gone off the deep end might be true, and that this would never have happened if they were under the command of his previous unit's leader. Astro, however, had no interest in Sanchez's biased views.
The team soon encountered a DARPA scientist, Zak Pennebaker, who explained that modified gorillas had gone rogue and attacked the carrier and base personnel. The Marines then came under attack from the gorillas, and Astro and the others were quickly forced to retreat. As they drove their commandeered troop transport truck to the flight deck, Astro helped to try and fend off their attackers, until Schofield and Bigfoot used the main gun of an abandoned F-14 Tomcat to cut down several of the gorillas. Schofield then ordered Astro's group to meet them at "Casper's door" while he drew the gorillas away.
Soon after they had reunited, Schofield realised that the gorillas were under the control of the Buck, and came up with a plan for them to defeat the gorillas. Astro, Sanchez and Bigfoot hid themselves behind the doors of an ammunition chamber on the island while Schofield and Mother lured the animals inside, with the intention of detonate the explosives. Before they could open fire, however, a DARPA scientist ordered them to stand down and appeared to congratulate them on their success. This was, of course, a ruse, and Astro and the other Marines found themselves on the wrong end of the Delta team's gun-sights.
Once Schofield realised a digital signal was how the gorillas were being controlled, Mother jammed the signal, freeing the gorillas awaken from their control. As they started attacking the DARPA scientists, Astro and the others took advantage of the Delta team's distraction to put them down first, before they flooded the tunnels and escaped. With that, Astro and the other surviving Marines waited for a plane to take them home.
In December of 2007, Astro accompanied Paul Robertson of the CIA to the Burj al Arab, as part of the United States' genuine wish to participate in a meeting concerning the approach of the Dark Star and the rebuilding of the Machine. Robertson assigned Astro to Jack West Jr's team, and as the tower was struck by a plane, Astro helped Jack and Stretch gather up their notes before parachuting off the building's helicopter pad to safety.
As their expert on the Machine, Max "Wizard" Epper, was being held at Xintan Prison by the Chinese, Astro helped supply the team information about Xintan so that they could break him out. Astro noted the risk they were taking to help Wizard, and asked Jack he would do the same if he were captured, to which Jack said he didn't know him well enough yet, but would see based on his loyalty.
After Wizard and Tank were liberated, Astro helped commandeer the Xintan Prison's chase chopper, and accompanied the team to Witch Mountain to retrieve the Philosopher's Stone, providing Jack with stun grenades to disbale Mao Gongli and his men. When this was done, Astro joined the second meeting on Mortimer Island, where they gained more information about the Machine.
As the team were making their way to the first Vertex near Abu Simbel, Astro was questioned about his country's knowledge about the Japanese's reputed pocession of a Pillar by Iolanthe Compton-Jones, who believed that Roobertson had informed him of America's attempt to seize the Pillar after World War II, but Astro was clueless.
At Abu Simbel, Astro helped the others search for the Vertex entrance, and through his underwater motion sensor belived to only spot crocodiles. Once Jack laid the Pillar, the team were surrounded by British forces, and Astro cursed himself for not realising that they were what had set off his sensor. Iolanthe left them to die by having him, Pooh Bear and Alby Calvin handcuffed to their sinking zodiac, but luckily Jack and Zoe Kissane arrived and freed them. In the chase to catch up to the Halicarnassus, Astro gave Jack his Armalite MH-12A Maghook to use. However there were forced to abandon their pursuit in order to allow the others to escape, and after ditching their vehicle they were apprehended by American forces, who drugged Astro.
Astro was taken to a mine in Ethiopia, still under the drugs' effects, and Wolf had two guards hold Astro up as he showed him to Jack, making it seem as though he had been working for Wolf all along. Once Jack was apparently killed, Rapier asked what should do with Astro, and Wolf replied that when Astro woke up, he would be given the choice to join them or die.
Astro woke up at the naval base on Diego Garcia, and was told that Robertson - who was actually in league with Wolf, and not the genuine American government who had authorised their association with Jack - was not supposed to have let him join Jack's team. Once he recovered, Astro was drafted into the CIEF forces looking to find the rest of the Pillars and Vertices.
When Wolf launched his assault on the Third Vertex's entrance at Hokkaido, Astro was among his forces. Astro tried to help Rapier, carrying the Philosopher's Stone, get to the entrance, but was unable due to the heavy fire from the Japanese. Luckily Jack, Zoe and Lily arrived and got Rapier to safety, and Astro was surprised to see Jack. Despite this, he followed him into the Vertex along with the other CIEF men, following his orders to open fire on the Japanese inside the Vertex without question. During their journey through the Vertex, they came across the trap containing the Vertex's Pillar, and were forced to wait until they could get access.
During their time waiting, Jack spoke to Astro, who didn't remember being in the mine and had been told that Jack had been planning to kill him and take the Pillars for himself. Jack realised that Astro had been tricked into infiltrating his team by Wolf and Robertson, and tried to tell him this. Astro was reluctant to believe it, but did inform Jack that he and everyone else was ordered to kill him once the Pillar was laid. He was part of the team intended to retrieve the Pillar from the trap, but was unable due to the Japanese snipers, and Jack got the Pillar instead.
Upon making it to the Vertex, Astro helped secure the boats Wolf and Jack were in using a cable winch with Rapier while they tried to lay the Pillar. However, a final attack from the Japanese saw Astro being heavily wounded. After the PIllar was set, Rapier assessed Astro's condition, and Wolf decided to leave him behind. Luckily for Astro, Jack was not so callous, and remained behind to help him back out of the Vertex. Astro thanked him for his help despite their being on opposite sides, and realised that Jack had been telling the truth. When they got out of the Vertex, however, they were captured by Russian forces.
Astro, along with the others, was taken to an old dam and observatory belonging to Carnivore, who had decided to step in on the mission to rebuild the Machine. The wounded Marine was placed inside one of Carnivore's formaldehyde tanks to be used as leverage for Jack's help, along with Zoe, Pooh's father, and Alby and his mother. Shortly after Carnivore abandoned the base, Wolf escaped his tank, and Astro was hopeful that he would release him, but Wolf didn't and instead left everyone behind.
While Jack defeated Carnivore at the last Vertex and repelled the Dark Star, Astro and the others were freed from their tanks by the rest of Jack's team.
Between The Five Greatest Warriors and The Four Legendary KingdomsEdit
Some years later in 2016, Astro was on tour in Kandahar, Afghanistan, back under Schofield's command. At some stage, Astro was asked to share his opinion on Schofield to a group of mysterious men who knew of his involvement in the Machine restoration mission. Soon afterwards, Astro, Schofield, Mother and Tomahawk were requested to perform a joint operation in southern Afghanistan with a small group of Delta operators led by Jeffrey Edwards.
As soon as they landed on an airstrip near a coast, Astro and the other Marines became suspicious of both the circumstances and the unperturbed Delta operators, but were soon forced to wear bags over their heads as they were driven to another location.
Astro would wake up some time later inside a train-mounted cage, and forced to watch as a mysterious man calling himself Hades announced the beginning of the Great Games of the Hydra, with Astro, Mother and Tomahawk being used to serve as hostages to ensure Schofield's participation.
- He was given the call sign Astro by his fellow marines due to his love of science fiction novels.
- Astro was the first character to appear in both the Scarecrow and Huntsman series, which at the time suggested that they were both set in the same fictional 'universe'.
- With the events of The Four Legendary Kingdoms, it is now confirmed that the characters from both series exist in the same universe.