Shadow weapon sealed/Box

Enlighten me please,

2 questions:
1. How/where do we get shadow weapon box?
2. How/where do we get sealed shadow weapons?

If theres a thread about this, please refer.

I see lots of shadow box around for sale but can't figure out where to get those

Also, quest from Ashen shadow instance gives already unsealed weapons as well as drops..

Thanks for anyone taking the time to answer this, been googling and can't find it

Shadow weapon sealed/Box