I think it'd be interesting if some of the relics would be obtained by first finding it broken and have to go through multiple steps to get it fixed up as opposed to just getting it as a rare drop from a chest or mob.

For example lets say to build Excalibur, you'd have to clear a fortress of monsters to find a chest that has a chance to give a Broken Sword Hilt. It would be worthless to sell, and there wouldn't be any really obvious clues as to what to do with it. But if you talk to the right NPCs in the world, you would find out that it was once part of a legendary sword. You would also find out that you need to search for certain metals and parts in order to fix it up, which leads to more dungeon crawling and searching.

Once you've gathered the parts, the relic item may be repaired by a legendary NPC of sorts. If we wanted it to be really interesting, under the guidance of this legendary NPC it could be revealed that the relic requires multiple crafters to put repair, and this would trigger a chance to set up a group crafting session to put the item together.