1) Craft 2 Godskull GS + 2 Carrion Krait Slayer (rare), 2 65s + 2 80s = chance for exotic. Any 4 rares in the past can upgrade to precursors. I also believe that creating dusk/dawn is related to time and not random. I kept getting dawns in the morning and dusks during the night time. I have no clue about whether exotics now can change into a precursor.
2) It costs 60 silvers when I initially crafted it. I can sell the exotics that I get for average 3.5 G even at 20% chance. You can't really lose money.
Basicamente, crafteaban 4 mandobles amarillos de lvl 80, los metian en la forja y tenian un 20% de que te salga uno exotico o con algo de suerte un prelegendario.