David Wheeler’s review published on Letterboxd:
Borrowing from Scandinavian folklore and co-written by Sjón—who is no stranger to the weird as he's often collaborated with the chameleonic singer Björk and written other stories concerning grotesque human-animal apparitions—Lamb [Dýrið; lit. "The Animal"] is a largely ineffective piece of modern folk horror, save for the eccentric premise and its complete lack of subjective filmmaking. One of the more interesting credits behind this frightfully austere, magical realist venture is Béla Tarr serving as executive producer (alongside star Noomi Rapace), which somewhat explains the funereal quality behind co-writer-director Valdimar Jóhannsson's direction, here in his feature film directorial debut after serving as, variously, an electrician or special effects technician in larger studio blockbusters. Jóhannsson's cold and stern style is welcoming—alongside cinematographer Eli Arenson's similarly ascetic yet beautiful camerawork—but his and Sjón's script work is decidedly lacking. It's orchestrated with a deliberate ambiguity that usually proves a winning asset, but such a spartan, tedious narrative, complete with uninspiring characters (with the tertiary brother perhaps being an unnecessary element altogether) and underexplored themes, makes it all tragically moot and strangely vapid, especially when it nearly threatens to be more farce than surrealist tragedy. Jóhannsson's form is reasonably promising, but his pen needs work.