Here's her story. It's long, I know, but, like I had said before, a fitting ending.
By the dawn of the 24th Century, the Constitutions were slowly being phased out of service in favor of newer ships sporting the latest in Federation technology, namely the Excelsior class. When X-Era technology was developed, it provided a glimmer of hope for the remaining Constitutions, and the realization of these hopes came with the U.S.S. Potemkin, but unfortunately, these hopes were short-lived. Although the Potemkin refit was successful, only a third of all remaining Constitutions in service were upgraded, while the remaining ships were allowed to serve out their intended service lives and then be decommissioned. Starfleet felt that the benefits of refitting the entire Constitution fleet to X-Era technology didn't out-weigh the costs involved. Around 2301, the Andromedan Invasion began, and ships that had been decommissioned and mothballed only a few years before were brought back into service, receiving a series of refits to increase their overall abilities. The invasion was brutal, with many ships on all sides either destroyed, or damaged beyond repair, with the Constitutions suffering heavy casualties.
After the invasion, all of the previously retired starships that survived, namely the Constitutions, continued in service only until newer ships came out of the shipyards to replace them, but after the Tomed Incident in 2311, Starfleet felt that the entire Constitution fleet, including those refitted with X-Era technology, had become too oudated, and were more of a liability than an asset in battle, and plans to retire all remaining ships of the class were slated to take place within 3 years.
In 2315, a desperate attempt was made to keep the Constitution design alive. Engineers and researchers took the salvaged secondary hull of a Constitution, repaired all the battle damage, reinforced the hull, and then mated the primary hull of an incomplete Warlock to the rest of the ship, to take advantage of the rail phaser array equipped in the saucer. Over the next 2 years, work continued on this experiment, and the ship received massive upgrades to every system, including weapons, shields, and warp drive. To generate additional power for the ship and to sustain higher warp speeds for longer durations, the engineers decided to equip the ship with a modified version of the LN-68 warp nacelles, sporting experimental technology intended for use in the next generation of starships. In late 2315, just as the remaining Constitutions in service were slated for retirement, the U.S.S. Anubis left spacedock to begin her shakedown cruise, but almost immediately serious design flaws appeared throughout the entire ship. The ship could not generate enough energy to power the weapons and shields effectively at the same time, while manuvering at even 3/4 impulse. The modifications to the warp engines made it very difficult to create and maintain a stable warp field. On one occasion, a near catastrophic disaster occured when testing out the new phaser systems, when an energy feedback loop threatened an overload in the phaser control systems. After only 4 months in space, the Anubis was recalled back to spacedock, and the researchers and engineers hoped to correct the design flaws, but after a year of trying, the project was scrapped, and the Anubis was placed in mothballs, and another attempt to refit the Constitutions wouldn't be made again until the launch of the U.S.S. Valiant during the Dominion War.
Nearly 56 years later, at the beginning of the Dominion War, the Anubis was brought out of mothballs and given a complete refit of her systems, which allowed her to finally live up to her intended design goals, and she saw immediate action, having taken part a few of the larger engagements during the war, proving her worth. When the Dominion struck deep into Federation space, the Anubis received a distress call from planet Betazed, and immediately responded. When she arrived, Jem'Hadar forces were beaming down to the planet, and also chasing after civilian evacuation transports from the planet. The Anubis immediately engaged the pursuing Dominion ships. In doing so, the Anubis came under heavy fire, and was eventually lost with all hands, but managed to buy the time the transports desperately needed to escape. After the battle of Betazed, the men and women aboard the U.S.S. Anubis were all posthumously awarded the Starfleet Medal of Valor, and after the war, a monument was erected on Betazed, paying tribute to all the brave Starfleet officers that gave their lives to the defense of the planet, with the crew of the Anubis being listed first.
The Anubis was the only ship of her kind, and after the war, her name and registry were given to a Sovereign-class starship, and that Anubis continues the legacy of honor, duty, and heroism that her predecessor left behind.