You need to be at least character level 20, before Boethiah will give you his quest.
You can't start the quest. You have to find the skulls on your own, with no map markers, and return them to the ghosts. The quest does not appear in your journal.
In Anvil, next to the Chapel. Talk to the priest outside.
You have to be Level 15+ then Bandits will start dropping them.
I don't know about Arena, Daggerfall and morrowind but in Oblivion you need to start the last thieves guild quest 'The ultimate heist' and in skrim it is part of the main quest.
You have to ask her for training, that should trigger the quest, or you could try speaking to Othrelos in the Elven Garden District. If neither works, then you've hit a bug.
I'm guessing a relatively high level... probably between level 25-30
run around imperial city and you should get the quest which will give u the location of shivring ilses :0
once u start get higher in level bandits and random bad guys will start wearing it
You need to be Lv20 to start the 'Pieces of the Past' quest.
go speak to the prophet outside the church in Anvil and he will send you on a pilgrim quest. when you have done all pilgrim points then you will start another quest. complete it and eventually you can get the relics =P
If you mean DAEDRIC armor, you need to be high level, at least level 24, and it will start appearing on Dremora and Marauders.
Once you get high enough level, like 15 or something, bandits will start carrying glass daggers, glass warhammers, you name it. It is based on level, not location.