The Supernatural Season 12 DVD set retains pretty much the same quality of many of the previous DVD sets, though not as good as the first 3 seasons' sets.
The season of course picks up from the aftermath of Chuck & Amara's patching of their feud with the resurrection of Mary Winchester & the introduction of the British Men of Letters. Plot-wise, Season 12 is the weakest by far of the entire series, though Lucifer did return to his old vessel thanks to the return of Mark Pellegrino who is brilliant as usual.
The season introduces Lucifer's son Jack who is finally born in the season finale and goes on to become a main element of Season 13. We also see Crowley return along with his mother Rowena, and of course everyone's favorite angel Castiel. One of the most interesting things of this season was the explanation of the yellow eyed demons, of which Azazel from the first 2 seasons was a part. We also finally see flashback scenes of what Crowley did to become the king after the events of season 5 and we also see the lance of Michael, which may return in season 13 or 14 considering the possibilities.
It should also be noted that Rick Springfield of 80's music fame makes a few appearances as one of Lucifer's vessels.
Even though season 12 was personally a letdown, I would suggest buying this for any diehard fan of Supernatural who wants a complete collection of the series on DVD. There are certainly some really good episodes in the set.