Returning to her home in Denmark, Bruun found herself plagued by nightmares and episodes of sleep paralysis, which she has described as "one of the worst times of her life."

They also wrote that "Where she could’ve bowed to the elitists and charged into heavier realms, instead she’s scaled back the extremity, revelling in the kind of heaviness that favours sensory impact over the hammering of guitars as she flits between English and Danish. "

In their review of the album, Decibel wrote that "black metal's just one of many textures manipulated by Bruun", and that her compositions "owe as much to Nordic folk music as they do to Ulver."

Dunn also enlisted Aaron Weaver of Wolves in the Throne Room for the recording sessions, who performs "the vast majority" of the drums on Mareridt.

AllMusic's Thom Jurek gave the album 4.5/5 stars and wrote very positive assessment, describing Mareridt as "a work of atavistic mystery, unflinching honesty, and balance.

Her delivery, full of sustaining notes that subtly decay, is reminiscent of choral music — with all the ritualism, religiosity and awe it entails.

"[16] Decibel wrote that "the album's heaviness requests validation from no genre, balancing frostbitten tremolos and end-days doom with nyckelharpa and mandola flourishes", concluding that "Mareridt isn't the embodiment of all that is trve, and it's a better record for it."