This is the harpy list I know of.
Its not very good: the combo pieces are not very good at winning the game individually, and its not very good at sifting to find the combo.
I played against some more traditional familiar lists that were running harpy, and they were ok: harpy does a good job protecting itself. It was more focused on making a massive board and beating down than comboing though, kind of like the simic familiar decks, but not as ramp focused.
The reason you want to run the black in familiar is
reaping the graves, which single handily beats all of the midrange and control decks in the format (and why this downshifting is probably bad for the format). Black raise dead effects make the combo very resilient, and reaping the graves it the best of the bunch. You also get
nightscape familiar, which reduces the cost of all of those 5cc spells, and blocks while you sift through your deck. Its also possible to run
chittering rats as a lock piece.
Familiar always ran an unusually high density of 3+cc spells, which are normally unplayable in pauper. Keep in mind that you were never actually resolving COF anywhere near on curve: it was generally a game ending threat.
Drake means a couple of things:
1. You can't do a mini-mana gush like you used to, as easily.
2. Its harder to respond to removal with
snap to protect your untapper.
3. You are more dependent on familiars to go off.
Which makes the deck more clunky, slower, and easier to disrupt.
In return:
1. You get a more difficult to remove threat
2. A threat whose stats are good enough to warp a board around itself.
3. You can either cut the bouncelands or the familiars. (which is a pretty big deal)
Keep in mind that the deck theoretically existed before, since with familiars you can chain
snap archeomancer for infinite mana. I just never saw a polished list, and knowing pauper thats probably just a result of it being a casual format with no incentive to brew and polish a deck.