- "The Forerunners were master shipbuilders, among other things. They were explorers as well, spreading across a galaxy of three million occupied worlds. It was not uncommon for them to find themselves in contact with other species and races with rudimentary ships such as yours. They utilized design seeds to build their own ships from local resources if necessary. But there were many occasions when resources could not support a design, so the Forerunners used whatever local vessels they could obtain and created an upgrade seed - hard light instructions, blueprints, if you will, which bonded to an existing structure, reinforcing the materials, molding them as needed, and upgrading components and systems."
- — 343 Guilty Spark explains the upgrade seed to the crew of the Ace of Spades.
An upgrade seed was a type of design seed utilized by the Forerunners to upgrade vessels of other species to have Forerunner technology upgrades within the ship's original framework of operating functional capability.
Design and operation
Upgrade seeds were designed to be tailored to specific types of vessels from races other than the Forerunners. The upgrade seed would not change the outer appearance of the vessel. Instead, the upgrade seeds would only strengthen its existing materials by hard light bonding. Inside, quantum and hard light filaments would intertwine with the ship's existing systems, directed by smart upgrade code, to create a custom integration between Forerunner technology and the ship's current specifications and technologies. As a result, the upgrades were limited by the limitations of the ship's original design. While the designs could be applied in orbit, it was better to ground the ship and run on auxiliary power as the upgrade seed did its work. 
While the upgrade seed could create an upgrade to the vessel's slipspace drive, it required a Forerunner slipspace flake like any Forerunner vessel did. The upgrade seed would then create a seamless intergration between the vessel's original FTL drive, Forerunner translight technology and the slipspace flake taking into account the materials available to work with and the size of the vessel. Other known upgrades that the seed was capable of granting included stealth technology, upgraded comms, weapons and navigation systems, all kept with the framework of its original operating functionality.
After hijacking the UNSC Rubicon in 2554,, 343 Guilty Spark intended to take the ship to the Etran Harborage to get an upgrade seed for the vessel, unaware that it had been destroyed in 2531 by the UNSC Spirit of Fire. However, the Rubicon instead crashed upon Geranos-a and was destroyed. After being rescued by the crew of the Ace of Spades, Spark decided to take the ship to the shield world and get an upgrade seed for it instead in order to continue his mission to find the Librarian. To help entice the crew's compliance, Spark offered them the opportunity to salvage from the planet. Following the destruction of the Etran Harborage debris field by a massive UNSC fleet, Spark explained his intentions to the crew and suggested that using an upgrade seed on the Ace of Spades would allow the crew to match the vessels of ONI and regain their personal property and the projections made by Little Bit of where the Spirit of Fire could've gone. After Spark revealed his history to them, the crew agreed to help him.
In order to get the upgrade seed, Spark took the Ace of Spades to the lost Forerunner world of Triniel which contained a Builder facility that had everything Spark needed to create an upgrade seed. After Rion Forge's touch as a Reclaimer activated the facility, Spark retrieved a slipspace flake from the laboratory where the crystal was cut. Spark led the crew to the lab where the design seeds were created where he input the design specifications for a Mariner-class transport ship and designed an upgrade seed for the human vessel while the Ace of Spades crew salavaged from the facility. Though originally hesitant to apply the seed, Rion agreed after being offered a deal by Agent Walter Hahn of ONI in order to give the Ace of Spades the advantage it needed with the upgrade process taking approximately eighteen hours, fifty-three minutes and eleven seconds. The cloaking technology the ship gained made it invisible to two searching ONI Prowlers which were also completely unable to catch up to or track the Ace of Spades when it jumped to slipspace. However, its cloaking was briefly penetrated by the AI Thea who detected a strange ship's signature on Earth that was registering as both human and Forerunner. Despite this brief penetration of its defenses, the Ace of Spades was never actually found by ONI and was able to spend a week on Earth undetected before departing right under the noses of Earth's Home Fleet. The Ace of Spades became a one-of-a-kind fusion of human and Forerunner technologies. Unlike other human ships with Forerunner technology, it was not a human retrofit but a seamless, unifying intergration led by Forerunner-driven technology.
List of appearances
- Halo: Renegades (First appearance)
- Halo: Renegades, page 177
- Halo: Renegades, page 210
- Halo: Renegades, pages 225-226
- Halo: Renegades, page 178
- Halo: Renegades, page 226
- Halo: Primordium
- Halo: Renegades, page 143
- Halo: Renegades, pages 143-146
- Halo: Renegades, Chapters 24-25
- Halo: Renegades, page 197
- Halo: Renegades, Chapter 28
- Halo: Renegades, pages 223-227
- Halo: Renegades, page 250
- Halo: Renegades, page 254
- Halo: Renegades, page 307
- Halo: Renegades, page 323
- Halo: Renegades, page 265