There is a Fight in sea where you go up agains Ultima and omega weapons. Ultima drops various peices which you then take to a NPC in Mhaura. Each peice of ultima has a corrosponding nashira peice. Trade for them at the NPC.
yes this is one of the only pieces of it that screams RDM the body is ok but only real benefit is the slight magic acc and dark skill. but these are very VERY nice for any of the jobs able to use. i will say smn kinda gets the short end of the stick for this set for the most part otherwise almost all of it is good for all the jobs listed