I actually didn't like the battle theme here all that much. Mostly just because the strings at the start seemed kinda OTT for a normal encounter. They create a tension which really isn't reflected in the fight itself.
It was less 'lets beat up some monsters!' and more 'fight for your life!'
Like it was mentioned before, this battle theme is used for encounters at night and apparently in caves/dungeons, where the battles are supposed to be much more difficult than normal daytime overworld encounters