Shadow of hate

At the location, the Shadow of Hatred decided to close the achievement on the Signs of the Vault and remembered the door closed by Darkness, and it was closed tightly. (beginning of location). I would like to ask the developers a question - do players need to be clairvoyant to understand how to open this door? I didn’t find any clues, and I didn’t find the key itself at the location. Even in WIKI there is not a word about this door. After a lot of poking around on the net, I found one message from a player that the door can only be opened with a Magic Arrow grenade (quite rare in the game). I went to the slaughterhouse in the Temple of the Killer for a grenade, where it often falls out, I didn’t take it before - it’s blue and the parameters are weak. The door can only be opened by throwing this grenade into the Darkness, if the Darkness is already destroyed, then all attempts to open the door are futile.
Spoiler