What's the song when Bishamon fights in episodes 11 & 12 of Aragoto? What is the name of the song in Noragami Aragoto episodes 11 and 12 when Bishamon fights? First, against Izanami in the underworld, and then against Kiun, the Thunder Dragon, immediately after rescuing Ebisu from a direct strike.
Assuming you mean the music that starts at about 18:18 in episode 11 and 16:25 in episode 12, that is "Distortion" from the Noragami Aragoto OST (disc 1, track 4). Here is a 20-second extract from the beginning of the track.