I have always loved playing black, because of all the removals, and the cool creatures, but I've always found that the cool spells and the cool creatures are just too mana hungry, and that's where devotion comes into play.
When I was playing the Mono-Black Devotion deck in standard a few month ago (Like 1 player out of 3 lol) I thought to myself that it was just too bad I couldn't play great cards like Phyrexian Obliterator or Vampire Nighthawk or even Griselbrand (I just love that card lol). So that's why I said to myself why not invest in one modern deck that you will truly love and have fun playing with (even though in modern, black devotion has no future whatsoever, but I only play with my friends so that's alright lol)
So here I am going to state the obvious and tell you why I chose the different cards that compose my deck, starting with the creatures.
Creatures
Bloodghast : A great two drops that gives me great early devotion and that is hard to get ride off because of its landfall ability.
Geralf's Messenger : Such a good card that gives great devotion (3) and deals two damages to the opponent as it gets into play. Plus it has undying, so the devotion is hard to get ride off and the effect that triggers when it comes into play will trigger a second time!
Gravecrawler : A super one drop that I can cast from my graveyard if it had been killed or discarded (see Liliana of the veil) if I have another zombi into play, which is totally doable seeing I have three creatures that are zombies (Geralf's Messenger, Gravecrawler and Gray Merchant of Asphodel)
Gray Merchant of Asphodel : One of my win cards. it does take time for me to build up some good devotion, but once it's done, it will hit hard! Everybody knows how hard it can hit seeing one player out of three used to play the Mono-Black Devotion a few months back lol
Griselbrand : I just love that card, it is just so great but it is a bit manahungry. That's why we rarely have the opportunity to play it, but with devotion it really is doable, and once into play it will allow me to draw extra cards to get to my win cards.
Phyrexian Obliterator : Do I really need to justify my choice here!? I mean a 5/5 trample for BBBB (Great devotion, loving it!) that induces the destruction of pretty much all your permanents if you dare try to stop it!
Vampire Nighthawk : Ok, the choice is simple here, Deathtouch, Lifelink, and flying, don't really need to say more.. oh and yeah, it gives good devotion too.
Planeswalker
Liliana of the Veil : This is just a great card. She will allow me to disturb my opponent without bothering me too much seeing I would probably be able to discard cards like Gravecrawler or Bloodghast (discarding Bloodghast would actually be the best outcome for me seeing that it would allow me to have it on the battlefield without paying its mana cost). She also acts as a removal that goes pass the hexproof by targeting the opponent. Of course if I want a specific creature to be affected by her, I would need the other ones in the way gone too otherwise it would not be as effective.
Other Spells
Geth's Verdict : a great removal for 2 that goes pass the hexproof and that deals one damage to the opponent targeted. If I do not deal with hexproof that much, I could run instead Victim of Night which is also a great removal in this format seeing there is not a lot of people running werewolfs, vampires and zombies. I can still switch it up for Go for the Throat if the player does run these type fo creatures.
Phyrexian Arena : Allows me to get cards faster, therefore to get to my win cards a lot sooner that expected, plus it builds up my devotion, and usually stays unnoticed by the opponent, which is still good.
Profane Command : Another of my win cards, that can really kill you in one blow. It is also very polyvalent and could allow me to react in different ways to the game. Can act as a removal if needed and can make my creatures pretty much unblock able. It can also double kill you if I bring back a Gray Merchant of Asphodel from my graveyard.
Thoughtseize : nothing to say really, just a very good card that has to be there, and could get me out of trouble before I even got into it.
Lands
Nykthos, Shrine to Nyx : Thank god this card exist otherwise this deck wouldn't lol
Urborg, Tomb of Yawgmoth : I am running this one just in the possibility that I would have in the very early game a Nykthos, Shrine to Nyx that would get me stuck on not having the black mana to get on the board Geralf's Messenger and so on.
So that's about it, let me know what you think, if should change stuff, give me your two cents, I'd be happy to have some feedback!!
Thanks everyone :D