A huge, unfamiliar Borg vessel that emerged from a spatial rift in 2401 asking for Picard and for Federation membership, and whose masked queen proved to be Agnes Jurati.
The ship appears in The Star Gazer, the opening episode of the second season of Star Trek: Picard. It comes through a green anomaly, dwarfing the Stargazer and the fleet around it, and sends a message asking to join the Federation. Its hooded queen beams to the Stargazer's bridge and starts to take over the fleet through the ship's systems, and Picard sets off the self-destruct.
The season returns to the same moment in Farewell. Having lived through events in 2024, Picard now recognises the queen's words and cancels the destruct order. She is revealed as Jurati, merged with the Borg Queen centuries earlier, leading a gentler Collective. She needed the fleet's combined shields to contain an energy burst from a new transwarp conduit, and her Borg become provisional members of the Federation to guard it.