An ancient culture whose interstellar archive, hidden inside a comet, nearly rewrote the Enterprise-D in its own image.
The D'Arsay are known only through the archive they left behind, a vast data repository hidden within a rogue comet that had drifted for some 87 million years. When the Enterprise-D studied the comet, the archive activated and began transforming the starship into pieces of D'Arsay architecture and artefacts.
The archive also took over Data, who channelled a succession of personas from D'Arsay myth, including the sun goddess Masaka and her pursuer Korgano. Picard ended the crisis by assuming the role of Korgano and playing out the myth to its conclusion, after which the archive restored the ship.