A neutral planet where two Klingon houses offer to discuss peace in 2256; the meeting is a trap, and Admiral Katrina Cornwell is taken prisoner there.
Cancri IV is a planet seen in the Discovery episode Lethe. During the Klingon war its people, who are neutral, agree to host a secret meeting at which representatives of two Klingon houses opposed to Kol say they wish to explore terms with the Federation.
Sarek sets out to attend on behalf of Vulcan, but his ship is crippled on the way by a bomber from a faction of logic extremists. With the opportunity about to be lost, Admiral Katrina Cornwell decides to take his place, although Gabriel Lorca, whose fitness for command she has just questioned, makes little effort to dissuade her.
On the planet the Klingons kill the Cancri hosts and Cornwell's escort and seize the admiral for Kol. Lorca, told of her capture, declines to mount a rescue without orders, and she remains a prisoner aboard the Ship of the Dead until Tyler and Burnham free her.