Diego was born on Madrigal. Diego had joined the Insurrectionists when he was younger. He began to plant bombs in spaceports, space stations, and passenger ships. He became a smuggler and a pirate. When Madrigal was attacked by the Covenant, Diego helped evacuate many people, including Maria Esquival and Ignatio Delgado. He took Delgado and Maria under his care. He lead the refugees to the Rubble, an Insurrectionist asteroid base orbiting Hesiod.
Diego helped the Insurrectionists improve the Rubble using spaceships and raw materials. He became a member of the Rubble Security Council. Diego helped establish the Exodus Project, a mass evacuation plan in case the Rubble was ever discovered by the Covenant or UNSC. In 2535, Diego attended Melko Hollister's funeral. He warned Delgado that a member of the Security Council was attempting to sell navigation data to the Kig-Yar.
Delgado was arrested by Council member Peter Bonifacio when he refused to hand over the navigation data. Delgado was interrogated by the members of the Security Council, asking for the location of the navigation data. The Council revealed that they were intending to place the data to the Exodus Project for safekeeping. Delgado reluctantly agreed and he brought Bonifacio and Diego to where the data was hidden, aboard his freighter, the Distancia.
When the three reached the freighter, Delgado was about to hand the data over to Esquival, but Diego was shot and mortally wounded by Bonifacio. Diego and Delgado were locked in the Distancia's damaged airlocks and left to die from lack of oxygen. Esquival succumbed to his wounds, but Delgado was rescued by Spartan Gray Team. Shortly after his death, Jai-006 put him in a cryo chamber to preserve his body until he could be safely transported back to the Rubble.
His sister, Maria, took his position on the Security Council after his death. When the remains of the Rubble arrived at the human colony of Falaknuma, a funeral for Diego was held on the planet.
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