Ouroboros serves two purposes: Idol worship, and representation of the Eclipse.

Eclipse is the original con job, if you didn't know:
1) Track star alignments, and learn when next eclipse is going to happen.
2) Convince everyone (including the king) that a monster is about to swallow the sun.
3) Tell them they only way it can be stopped is if they give you all their wealth, so you can cast a spell on the monster.
4) everyone laughs at you, until the eclipse happens.
5) Suddenly, every sucker in the kingdom gives you their wealth, so you can cast your spell.
6) You say "Avarah Kadavrah" (the original pronunciation from freemasonry) and the sun comes back.
7) You are now the most powerful person in the land, and the peasants praise your name in song.