This isn't the first time Bethesda have included a reference to Katatonia - Skyrim had one too. On a terminal in an abandoned military base, you'll find the ramblings of its former inhabitant who describes his descent into apparent madness as he hears strange sounds while browsing various radio frequencies. In actuality, the whole diary entry is one big nod to the Swedish metal band. The letters 'D-E-K' refer to the band's 2012 album Dead End Kings, and the sergeant's name - J. P. Renkse - refers to Jonas Renkse, a member of the group.