- "Listen to me, Covenant. I am Vice Admiral Preston J. Cole commanding the human flagship, Everest. You claim to be the holy and glorious inheritors of the universe? I spit on your so-called holiness. You dare judge us unfit? After I have personally sent more than three hundred of your vainglorious ships to hell? After kicking your collective butts off Harvest - not once - but twice? From where I sit, we are the worthy inheritors. You think otherwise, you can come and try to prove me wrong. Is that the best you can do? Watch what one unworthy human can do!"
- — Admiral Cole's last known transmission directed to the Covenant fleet above Viperidae.
The Battle of Psi Serpentis was a battle fought toward the latter half of the Human-Covenant war in 2543 and had become colloquially known as Admiral Cole's Last Stand due to the presumed death of Admiral Preston Cole. The actions of Admiral Cole and his fleet in the battle rival the accomplishments made by most other heroes of the war.
Cole spent a great deal of time preparing for the battle. The Admiral ordered massive amounts of Titanium-A plating for his flagship, UNSC Everest; acquired the UNSC Io which had previously been damaged in the Battle of 18 Scorpii; and did extensive theoretical studies of star density and slipspace travel. The purpose of these activities were unknown to Cole's superiors and the UNSC at-large at the time. Cole also procured massive amounts of ordnance for the conflict, including 105 Shiva-class Nuclear Missiles, 2400 Archer Missiles and 45,000 blocks of AAA Helix system ammunition. In addition to these actions, the prowler UNSC Wink of an Eye prepared the battlefield in the Psi Serpentis System for a week by observing the Covenant's activities in the system. Finally, Cole appears to have contacted his former lover and Insurrectionist Lyrenne Castilla, who had recently reappeared at the Battle of 18 Scorpii, in an attempt to coordinate independent participation in the battle.
Battlegroup India jumped into the Psi Serpentis system as a single unit, the resulting wave of radiation rippled through the system and encompassed the three nearest planets. This was a clear warning sign to the waiting Covenant fleet, which swiftly moved to engage Cole's forces. The UNSC battlegroup then performed a previously unheard of in-system jump to the gas giant Viperidae. A dozen ships limped behind the main task force due to the random inaccuracies of UNSC trans-light engines and many were picked off by the Covenant, however this small distraction allowed Cole's force to regroup. As the Covenant fleet bore down on Battlegroup India, Cole divided the fleet into two groups, the starboard most of which arced around Viperidae to cut into the pursuing Covenant fleet. The majority of Cole's fleet was able to bring their guns to bear on a now divided Covenant fleet. Cole's forces inflicted heavy damage on the hundred or so Covenant vessels, destroying 23 enemy vessels while losing a third of the fleet.
The Covenant fleet regrouped and pursued Cole's fleet until a group of Insurrectionist vessels emerged from slipspace. Led by the heavily modified Bellicose, they opened fire on the Covenant, losing a quarter of their number. Once they attacked they smashed through the Covenant formation and withdrew from the system. Cole himself moved Everest deeper into Viperidae's gravity well while the UNSC fleet proceeded to disengage. The Admiral then issued a broadcast to the pursuing Covenant ships, boasting of his own achievements while scoffing at their claim to righteousness. Sensing and accepting the challenge, the Covenant moved to attack Everest, but their plasma was deflected by the magnetosphere of the planet.
Cole moved Everest past the point of no return from Viperidae's gravity well, and launched a barrage of missiles at the lead ship in the Covenant formation. Nuclear fire destroyed the ship but there was little damage done to the rest of the fleet. Unknown to the Covenant, Cole had launched one hundred Shiva nuclear warheads into Viperidae's unstable core. The resulting fission event caused the planet to briefly go supernova and become a brown dwarf. The resulting shockwave obliterated all of the Covenant ships, reduced Viperidae to a smoldering rock, and presumably destroyed Everest.
In addition to the alleged death of Cole, over 300 Covenant vessels, two fleets, were completely destroyed when UNSC nuclear missiles detonated inside the atmosphere of Viperidae. However, the light show that Cole gave the Covenant, prior to the micro-nova of Viperidae is suspect. A group of Archer missiles prematurely detonated in front of Everest, and seemed to mimic a slipspace rupture. Prior to the battle, Admiral Cole had done extensive research into slipstream travel which, when reviewed, appeared to be the calculations for an in-atmosphere jump. The next shot of the cruiser, captured by the retreating battlegroup, revealed the silhouette of another vessel, presumably the Io. After another flash of light only one ship remained, and was consumed by the nova event.
This has left Admiral Cole's death subject to much speculation, and AIs under Codename: SURGEON's command calculated that there was an 89.7% chance that Cole had indeed escaped in an in-atmosphere slipspace jump. Either way, Cole's achievements in this battle alone were only rivaled by the destruction of the Unyielding Hierophant and the actions of John-117 throughout the course of the war. July 28, 2543 was declared a day of mourning in the wake of Cole's apparent death. A painting depicting the battle, titled "Admiral Cole's Last Stand" was created, and by 2552 it hung on the wall of HIGHCOM Facility Bravo-6 on Sydney, Earth.