I started watching Attack on Titan and this song started playing in slow motion when the "Female Titan" showed up at Levi's group, around 20:30 of episode 18.
What song is this?
Well, I did some digging, and this is what I found out. Shazam identified the song as: 進撃st-Hrn-Gt-Pf20130629巨人
by 澤野弘之.You can also find it under the title" Rittai Kidou Remix". Plz listen and correct me if I am wrong because I have also found other tracks as well. But this one was the most accurate, according to my listening experience.