Yeah i get it IF U dont have a lot of time but u can get a random one from dismantling a gear or weapon. U get some from dismantling a already masterworked gear or weapon. There r bounties u can get cores from. Spider has some, okay, it doubles but i buy 1 or 2 from spider each day. But u do get enough legendaries to dismantle. With the change to crucible, dont know if they changed the rank system up on that as if u fully rank out u get 10 cores..