|“||We will stay and fight. We are Shadowhunters. We cannot all flee and leave only the worst of us to seize power. We must resist.||”|
–Diego, Queen of Air and Darkness
Diego grew up in Mexico with his family and showed promise as a skilled Shadowhunter. He attended the Scholomance at a young age when it was reopened after the Dark War; he graduated soon after and became one of the youngest ever to become Centurion.
Diego fell in love with his childhood friend Cristina Rosales. The two eventually entered a relationship and had plans to marry, while she also planned to become parabatai with his younger brother, Jaime. Cristina's mother greatly approved of their union.
When the Cold Peace began, the Rosales families were told to surrender a powerful heirloom, among other gifts from their hadas connections, to the Clave, particularly as the Dearborns and the Cohort began to demand it. Instead of turning the heirloom over directly, they falsely told them that only a Rosales could make the object work.
In May 2012, he and Jaime were at the Rosales residence at San Miguel de Allende with Cristina. One night, an intoxicated Jaime told Diego of his ill intentions with Cristina, while Diego remained silent to let him talk it all out. Diego meant to warn Cristina during Jaime's trip to Idris but never got the chance because Cristina, who overheard Jaime's rantings that night, fled to Los Angeles to get away from them, her sudden departure devastating and surprising him, clueless to why she did so.
With Cristina and their strongest connection to the D.F. Institute gone, they became more pressured to give or hide their heirloom. To delay the Dearborns' demands for the heirloom, Diego tied himself to the Cohort in an arranged marriage to Zara Dearborn, while Jaime took the heirloom and went into hiding.
When Diego heard of reports of necromantic magic activity in Los Angeles, and of Emma Carstairs's belief that her parents were killed by something other than Sebastian Morgenstern's army, he went to investigate on behalf of the Scholomance. He first visited the Los Angeles Institute to talk with the head, Arthur Blackthorn, but was immediately turned away. Deciding to investigate the matter on his own, he bought weapons at the Shadow Market, specifically from Johnny Rook, who tricked him into buying bolts tinged with belladonna poison.
The investigation led him to the body drop behind the Sepulchre Bar, shortly before Emma and Cristina arrived at the scene to investigate as well, though they never crossed paths. There, she found Followers of the Guardian beating Ava Leigh and stopped them. Ava Leigh escaped and he tracked her down to the house where she lived with her boyfriend, Stanley Wells, who was also the latest victim of the killings in L.A.. While there, Emma and Julian Blackthorn arrived; not recognizing them, he assumed them to be the murderers. He hit Julian with his bolts, not realizing that he was a Shadowhunter and that his bolts were deadly poisonous, and fled when Emma gave chase.
While chasing down Casper Sterling, one of the Followers, he ran into Emma and Cristina. He was shocked and delighted to see Cristina again. He later fought alongside Cristina, Emma, and the Blackthorns to rescue Tavvy Blackthorn and prevent the warlock Malcolm Fade from sacrificing the former to resurrect his lover, Annabel Blackthorn.
When the Clave was finally alerted to the recent events, Diego stood by his decisions and testified to Robert Lightwood that he believed that the Blackthorns' did what was necessary. Robert decided not to punish Diego or strip him of his position because he was supposedly one of their best warriors. After clarifying to Cristina the circumstances of Jaime's statements, the couple reconciled.
Search for Malcolm
In response to the sudden surge in sea demon activity in L.A., suspected to be connected to Malcolm's death, a large group of Centurions arrived to stay at the L.A. Institute to search for Malcolm's body and the Black Volume of the Dead, which went missing at sea after his deadly confrontation with Emma. Diego's initial delight turned into dread when the group included Zara, his fiancée, thus ending his just rekindled relationship with Cristina.
One evening, after several nights of fruitless searches, Malcolm himself attacked the Institute with a horde of sea demons. Malcolm demanded a Blackthorn sacrifice, prompting them to flee, leaving Diego and the other Centurions to remain and fight off the demons Malcolm set on them.
Cristina ended up at the London Institute with Emma and the Blackthorns. Unable to contact her because of how close Zara was watching his every move, he passed a letter to her through Jaime, instead.
Some time after—upon Arthur and Malcolm's deaths, with Zara claiming the responsibility and honor of the latter—at a Council meeting for Annabel Blackthorn and Kieran's testimonies, Diego attended with the other Centurions. Cristina finally spoke to him, no longer angry but also now accepting that she was no longer in love with him. Wanting to be prepared for the worst, Cristina asked him to protect Kieran and take him to the Scholomance with him should something go wrong at the Council meeting.
Following the panic after Annabel's killing spree at the meeting, Diego did as he had promised Cristina and took Kieran to the Scholomance. He successfully hid Kieran for a number of days, with the help of his friends Divya Joshi and Rayan Maduabuchi.
When Zara Dearborn and her group returned from Idris, however, they caught Kieran and tried to torture him in the Hollow Place. Samantha Larkspear tripped and fell in, and the water made her relive every awful memory of her crimes. Kieran pulled her out, but the Cohort put the blame on him and tried to take him back to Idris. Diego and Kieran ran to the library, where Kieran summoned his faerie steed Windspear. Though Kieran asked Diego to escape with him, Diego decided to stay and fight.
Diego and his friends were taken into custody and brought before the Clave, claiming that they helped Kieran escape after he had harmed Samantha. Because the Cohort drew Quietude runes on them, they were unable to speak up on their defense. While imprisoned in a cell at the Gard, Dearborn released a statement declaring that they were traitors. The news reached his brother, Jaime, who immediately came and was thrown into the same cell as him, bruised and beaten up; Zara tried to use Jaime's safety in an attempt to get the location of the Eternidad from him.
As Jaime's wound got infected, Diego begged the Cohort for him a stele so that he could heal his brother, to no avail. Eventually, Anush Joshi slipped him a stele while delivering food for them; Anush noted that Diego had been the only one who was kind to him at the Scholomance and told him that he planned on joining the resistance.
The night before the Cohort's parley, Dru Blackthorn picked the locks to the Gard prison and broke Diego, Jaime, Divya, Rayan, and the Consul, Jia Penhallow, out. The group made their way to Diana's Arrow where they took up arms and gear in preparation for the battle they knew was coming.
On the battlefield, Diego found and saved Kieran from a Rider of Mannan, Delan. Following Jia's instructions, Diego and the others put up a Malachi Configuration to contain any of Dearborn's followers that they could capture without resorting to killing. Just when he captured Zara and put her in the makeshift prison, a redcap appeared and struck him in the face with a pike, knocking him out. The redcap dragged him across the field before Jaime found him. When he woke up, Diego tried to insist that he would go on fighting, but Jaime refused; Diego eventually relented and let his brother heal him.
At one of the Clave meetings after the battle, a recovering Diego recognized and pointed out to Jaime that the guards escorting the Cohort prisoners were Cohort sympathizers. Refusing to accept the Clave's ruling on their punishment and Alec Lightwood's appointment as the new Consul, the Cohort staged a mutiny, proclaiming that their Clave would go on within Idris, welcoming any believers of their cause, or else they would all kill themselves. Diego and Jaime, prepared to return to their home in Mexico, were among those who immediately left.
At Alec and Magnus's wedding around three weeks after the meeting, Alec offered Diego the position of Inquisitor. Diego expressed his doubt that he deserved the position to Cristina, and the girl convinced him otherwise. Diego and Jaime then decided to entrust the Eternidad with Cristina.
Diego is widely thought to be very handsome. He has thick, dark hair, dark eyes with high cheekbones, olive-toned skin, broad shoulders, and is very muscular.
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Diego is a masculine Spanish name, possibly a shortened form of Santiago, which means "Saint James", derived from Spanish santo "saint" combined with Yago, an old Spanish form of James, the patron saint of Spain. In medieval records, Diego was Latinized as Didacus, and it has been suggested that it in fact derives from Greek διδαχη (didache) "teaching". Diego is also considered the Hispanic version of James—primarily due to their connection with the biblical character Ya'akov (Jacob)—which means "supplanter; he that replaces".
His maternal surname Rosales was derived from the Latin word "rosa" and is the plural form of the Spanish word "rosal", both of which mean "rosebush". His paternal surname Rocío is of both Italian and Spanish origin, where it means "dewdrops", or simply "dew".
- Diego's favorite meal is breakfast, to the point where he also enjoys having breakfast food for dinner. When he was growing up, he would often get up early to surprise his family with chilaquiles.
- Diego's favorite weapon is the axe.
- He was initially set to be younger than Jaime.
- It has been implied that Divya Joshi is Diego's new love interest.
- Lord of Shadows
- Queen of Air and Darkness
- Lady Midnight
- A Love That Never Tires, a Queen of Air and Darkness extra
- Behind the Name: Diego and Santiago
- How Are the Names 'James' and 'Diego' Related?
- Diego on SheKnows
- Rosales on Familycrestdb
- Meaning of Rocio
- Rocío on Baby Name Wizard
- Archive of surname explanation Tumblr post
- An Illustrated History of Notable Shadowhunters & Denizens of Downworld
- "16 and 18." Cassandra Clare on Twitter
- "Diego is younger." Cassandra Clare on Twitter
- "I think if you look closely you can see who his new love interest is in Queen!" Cassandra Clare on Tumblr