Featuring additional production and programming by Arca, mixing by The Haxan Cloak, string and vocal arrangements by Björk, and a four-person group of cellists, "Black Lake" consolidates a dramatic sound with cellos and electronic beats that fade and reappear throughout the song.

"Black Lake" received critical acclaim for its lyrical depth, sonically tense and vivid beats, and lively pace, thus leading to several finding it to be the focal point of Vulnicura and a departure for Björk amidst a career that was often found to have previously been more detached thematically.

The accompanying music video for "Black Lake" was directed by filmmaker Andrew Thomas Huang and represents Björk's sorrow and timeline of emotions as she travels through Iceland's barrens from a dark and volcanic chasm to a lush basin.

[11] Its lyrical composition describes the aftermath of her separation from ex-partner Matthew Barney,[12][13] with verses including lines such as "My soul torn apart / My spirit is broken"[14] and "Family was always / Our sacred mutual mission / Which you abandoned".

[14][33] Will Hermes of Rolling Stone praised the "knife-twist" lyricism of "Black Lake", and opined that it was Vulnicura's "most devastating number" as it unfolded "in slow-mo",[19] while Jason Lipshutz of Billboard remarked that with the song, Björk let out "the fluid fury of a woman scorned.

"[3] Vogue's Alex Frank found that the "descending strings and bubbling techno beats" of "Black Lake" could make one "imagine falling into a body of water as dark as a computer screen.

"[34] The Line of Best Fit's Robby Ritacco highlighted the song's "brooding tension" and praised it for "unleashing all five stages of grief in near unison",[35] whereas Vox's Kelsey McKinney commended Arca's beats that she found to "sonically stab" throughout "Black Lake", alongside the following tracks "Family" and "Notget".

[22] Lindsay Zoladz of Vulture praised both how "stingingly precise" each verse was in its detail, given how Björk's character was typically "distant" and "eccentric", as well as how she perceived the song as "soaring heart-first into an explosive crescendo".

[36] Sam C. Mac of Slant Magazine found the song to be a "frigid pasture of Homogenic's glacial continent", its violinic sound "reminiscent of Mihály Víg’s hauntingly cyclical scores for Hungarian filmmaker Béla Tarr", and its 10-minute length "summoning the apocalyptic expansiveness of epics like The Turin Horse and Sátántangó.

"[10] The music video for "Black Lake" was directed by Andrew Thomas Huang, commissioned by the Museum of Modern Art (MoMA),[37] and filmed in Iceland over three days in July 2014 at the Fagradalsfjall volcano (approximately half an hour from Björk's home), in the middle of the night.

Liv Siddall of Dazed said it was "the lovechild of a guild of some of the most talented and Björk-ready artists working today,"[48] while Rolling Stone's Jon Blistein called it "beautifully intense" and expanding of her "long line of striking music videos".

[44] Jamieson Cox of The Verge additionally remarked that the video made "for a draining, memorable viewing experience",[45] and Stereogum's Gabriela Tully Claymore added that the lack of any mask on Björk's face affixed "an extra layer of exposure to the already raw song".