Oldie but a goodie.

Creo 2?  Yeah, I haven't seen that in a long time.  Refresh my memory, what makes that layer show up again?

Dean,

If I am not wrong, this layer will create when you will hide something from model tree (e.g. Datum) and export (STEP). When importing that data, BLACK_HOLE layer will be there for hidden items as Creo will not export Hidden Layer.

Don't let it grow too big!