I've heard that you can get clear devil spar from the abysmal devils in the training area, however I'd do the red cow method if it's been confirmed before. I might learn superior afterall since I plan on making blue monster clothes for the quest that have monsters that do magic attacks since it is mdf + atk which is far more practical then using a thorn suit purely for atk (and looks) reasons. However since I already have goddess skill and steam boat design I still don't think the worst magic attack monsters are behind me.

When going for devil spar pieces mammoths are probably your best bet.

Also is there any guide somewhere to all the star quest?