One of the most intriguing aspects of the Bird Box series is the enemy humanity's facing. This comes in the form of mysterious creatures, which -- once people cast eyes on them -- push folks to commit suicide. The first film in 2018 never explained how this was possible or where they came from, leaving fans curious if Bird Box Barcelona would reveal their secrets.
Source：https://www.cbr.com/bird-box-barcelona-big-twist-seers-monsters/
