T'Kuvma's ancient, massive Klingon flagship, the ship of the dead, which helped spark the Federation-Klingon War of 2256 at the Binary Stars.
The Sarcophagus was the enormous flagship of T'Kuvma, an ancient vessel whose hull was covered with the coffins of fallen Klingon warriors. Also known as the ship of the dead, it carried a cloaking device that allowed it to hide from Starfleet sensors.
In The Vulcan Hello and Battle at the Binary Stars, T'Kuvma used the ship's beacon to summon the Great Houses and confronted the USS Shenzhou. In the battle that followed, T'Kuvma was killed when Michael Burnham and Philippa Georgiou beamed aboard, and he became the martyr whose message united the Houses for war. The crippled ship was left at the Binary Stars, where his followers Voq and L'Rell survived aboard it for months.
The ship was later restored and taken over by Kol of the House of Kor, who made it his flagship and used its cloak to devastating effect. In Into the Forest I Go, Discovery's crew broke the cloaking technology and Burnham fought Kol aboard the vessel, after which Discovery destroyed it.