Raider
It stays silent, the air seems... Breathable? But only in the area you are in, there seems to be a giant bubble, protecting the area.
There is no responds, only a faint signal coming from the stronghold in the distance. The signal began to grow fainter and fainter, until it dissapears... Seems they know you have arrived, and they presume you can arrive without any signals.
Once you walk closer, the fortress seems quite big, with a door of 6 meters tall. colored black with red markings, and a dim light coming from the inside.