nuclear-capable underwater drone called Ocean Multipurpose System Status-6.
Defense News Reports that “A draft of the Pentagon’s Nuclear Posture Review confirms the existence of an underwater nuclear drone made and operated by Russia, a capability the U.S. Defense Department had not previously publicly acknowledged.”
Maybe this is another reason we might want to add an ASW capability to our ships.
(Perhaps we have someone out there who can translate the info on the graphic above?)
Chuck Hill's CG Blog 
This was leaked by the Russians back in 2015. I wonder why it took so long to acknowledge.
http://freebeacon.com/national-security/cia-leak-of-nuclear-armed-drone-sub-was-intentional/
It even has its own Wikipedia page: https://en.wikipedia.org/wiki/Status-6_Oceanic_Multipurpose_System
Some discussion here: https://www.aspistrategist.org.au/russian-nuclear-torpedoes-impact-on-the-law-of-the-sea/
As far as I am concerned, if one of these is detected, it is a weapon and it is fair game. Destroy on sight. The complication is how to tell the difference between this and other unmanned under water vehicles.
More on the Status Six here: http://www.navyrecognition.com/index.php/news/defence-news/2018/march-2018-navy-naval-defense-news/6021-status-6-russia-s-new-intercontinental-nuclear-armed-powered-autonomous-torpedo.html
Reportedly these will be operational on two nuclear submarines with initial operational capability in 2027. https://www.navyrecognition.com/index.php/news/defence-news/2018/may-2018-navy-naval-defense-news/6224-russian-navy-to-receive-poseidon-status-6-nuclear-powered-uuv-by-2027.html
More information on the weapon. Its larger than originally thought.
http://www.hisutton.com/Posiedon_revealed.html
More information on the weapon including speed–100 knots. Also Chinese extra large underwater unmanned vessels. https://nationalinterest.org/blog/buzz/china-studying-russias-robot-submarines—and-building-one-their-own-27237
covert shores has some thoughts on countering these. http://www.hisutton.com/Countering_Russian_Poseidon_Torpedo.htmlountering these.
Reasons to believe the max speed is more like 60-70 knots. http://www.hisutton.com/Poseidon_Torpedo_Supercavitation.html
A bit more evaluation of numbers and capabilities. http://www.hisutton.com/Poseidon_demystified.html
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Discussion of the possibility of a seabed launched version.
http://www.hisutton.com/Akademik-Aleksandrov.html
Another submarine to carry the weapon. http://www.navyrecognition.com/index.php/news/defence-news/2020/may-2020/8389-russian-navy-project-09851-khabarovsk-nuclear-submarine-to-be-floated-in-june.html More to come.
to be tested in the Arctic. https://asiatimes.com/2020/05/russia-set-to-test-doomsday-drone-in-high-arctic/
An evaluation of how it might be used.
https://www.realcleardefense.com/articles/2020/07/25/the_barbarians_in_the_bay_russias_nuclear_armed_drone_submarine_115493.html
“Poseidon Nuclear Torpedo Trials Close To Completion” https://www.navalnews.com/naval-news/2020/07/russian-mod-tsirkon-hypersonic-missile-poseidon-nuclear-torpedo-trials-close-to-completion/
The new submarine designed to use the “Status 6”
http://www.hisutton.com/Khabarovsk-Class-Submarine.html
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Base ready Summer of 2022 https://www.navalnews.com/naval-news/2021/01/russias-poseidon-nuclear-torpedo-base-to-be-ready-by-summer-2022/
Submarine designed for this system. https://news.usni.org/2021/02/25/new-details-of-russian-belgorod-doomsday-submarine-revealed
Russian TV Segment On Poseidon Nuclear Torpedo Destroying Britain Is Misleading http://www.hisutton.com/Russia-1-TV-Segment-On-Poseidon-May-1-2022.html
Report of delivery of the first production batch. Some speculation there could be a conventional warhead variant. https://www.thedrive.com/the-war-zone/russia-has-built-its-first-production-batch-of-poseidon-nuclear-torpedoes-report