That's the infamous "duckbill".
All the wires coming out of the right side of that thing aren't actually wires, they're fusible links. That thing can cause all kinds of problems, if you haven't had any trouble yet expect the same sort of trouble from the orange wire 2nd down from that pic when you lose all your key-on power.
No real wiring diagram to be had from it, those two wires on the left split into all those fusible links. I'll check my diagrams later tomorrow and update this with specific uses for each wire.