If it's fought in Necropolis, either Crusade or Cerebrum Dispersio will play, while if it's fought in the Ashpit, Juggernaut will play.
Where it might reemerge can be generally determined by the direction its seen travelling just as it begins to burrow, however this is not always accurate and most likely due to a bug: it can sometimes appear in a location it did not appear to be travelling to. Lyrics, Song Meanings, Videos, Full Albums & Bios: Morituros, Fundamentum, Cerebrum Dispersio, Cicatrix, ReGenesis, Nativitate, Pulso Profundum.It also cannot appear on any of the alternate Chapters added in Repentance.
It will generally try to reemerge close to Isaac or directly in his path to cut him off. The Fallen is a boss that can appear on any main path Chapter, with the prerequisite that Isaac has entered (not just encountered) a Devil Room through any methods, and with the following exceptions: It cannot appear on floors with predetermined bosses such as Mom, Mom's Heart, Isaac, etc. The Pile repeats this attack 3 times in a quick succession. Burrows underground, then quickly reemerges elsewhere in the room and fires 5 bone projectiles in a spread towards Isaac.The Pile slowly slides around the room slowly and performs the following attacks: