This is basically my casual take on black devotion ... well, actually just Gray Merchant of Asphodel. The idea was to get as many permanents with black casting cost into play as possible, obviously, but since I play multiplayer exclusively (mostly Pentagram) I went for durable and recurring permanents.
The core:
Geralf's Messenger drains himself and comes back once via undying. Luckily he happens to be a zombie, so he enables Gravecrawlers to come back, too. Fog Gnats grant solid defense against anything that doesn't trample. Phylactery Lich is especially awesome because it provides no less than 3 black and is indesctructible - IF you have an artifact.
There are lots of other support cards. As usual, running one-ofs is just my style, I want to make use of my collection. And in some cases I just don't own more than one copy.
For once I am foing with basic lands only - simply for the reason because I just can't use neutral mana!
THINGS TO IMPROVE:
* Biggest issue for me right now is the Phylactery Lich. As great as he is, he requires artifacts in play and artifacts don't add to my devotion count. Well, the scepter of Fuck does but 1 is all I own ... I am also unsure if Charcoal Diamonds are the way to go because I have so many cc2 and cc3 cards, I don't gain much from playing one second turn (however, they accelerate the Merchant one turn).
* Second concern is about the Merchant itself. I have zero ways to tutor and just one card to get him back (the Delver), this is probably not enough. On the other hand I also don't want to be "that guy" that has an engine where I play a Merchant every turn because then I get ganged up against as soon as they recognize the deck - and that's something you generally don't want and especially not in a mono-black deck whose mana curve ends at five ...
* I have a decent kill and have covered life gain, there is also a bit of card draw. Apart from that I lack almost everything else a multiplayer deck needs, graveyard hate, recycling, removal, a reset button. But whatever it is, it should fit the theme. That's why I added the single Gate to Phyrexia I have.
Gameplan is simple, get permanents into play to raise your devotion count and if that's high enough, play Gray Merchant of Asphodel for a huge Drain Them All Life. Typically you want to cast one when you have 8 black mana symbols because that means 2 Merchants + one Messenger = 20 damage but as I said earlier, you don't have tutors or ways to reanimate Merchants, so maybe you only see a single Merchant all game. You can also attack of course, but be careful with this, you don't want to lose creatures. Better play safe.
SINGLE CARD CHOICES AND STRATEGIES:
Blood Ghast:
Nice recurring 2 black mana symbols. You might want to keep a land in your hand for the turn you play Merchant.
Erebos Titan:
Nice pick of the newer cards. He will probably never become indestructible in multiplayer but that's irrelevant - 5/5 for 4 mana is pretty decent (in the good old days this would require a drawback and was still powerful, Juzam Djinn was once the most expensive creature card), he provides 3 black mana symbols and has a decent chance to come back from the grave in multiplayer.
Gatekeeper of Malakir:
Yeah, it's random to run a single one, I just wanted to play him.
Kiku, Night's Flower:
Stumbled about her during card search, had never heard about here before, but nice pick! All those fat creatures with crazy abilities you see these days ... Kiku just politely asks them to fuck themselves.
Nantuko Shade:
Was once a powerhouse in Type II and quite expensive, I picked one up recently for cheap and wanted to play it, finally, after GASP! 14 years ...
Phyrexian Delver:
Great way to use a Merchant a second time - only use him on something else in an emergency! He costs life to use, however, the Merchant will gain you more than that (it'll drain everyone for at least 4!).
The Delver is a zombie, BTW, so he enables Gravecrawlers.
Uncle Istvan:
I own an original one from The Dark, signed and all. This is finally a deck where I can put him to good use, three black mana symbols and won't die in creature combat!
AEther Vial:
The deck isn't high on the mana curve but many cards require additional mana to use, so you can save up some there using the vial, setting 2 counters and later maybe a third. If the game goes into late game you might want to go all the way up to 5 counters, that way you can a) play the Merchant at instant speed and b) play a lot of stuff before putting Merchant into play.
AEther Vial also provides a target for Phylactery Lich's counters, however, only do this if there are no other targets! AEther Vials are juicy targets for removal spells anyway, if you put the phylactery on it, you'll lose two precious cards at once.
Phylactery Lich:
Talking of him, remember that you can always put the counter on an opponent's artifact, he would have to destroy his own artifact in order to get rid of the Lich.
Glistering Oil:
This is mostly here because it provides two black mana symbols and keeps coming back. Secondary uses would be to kill small opposing creatures (yes, you can play it on opponent's creatures) and to put it on your own creatures in order to wear down opposing blockers with regeneration, indestructible etc. It's also of great use on Geralf's Messenger to negate the +1/+1 counter from undying. But, of course, you could also slap it on a Lich or the Titan to kill somebody via poison!
Underworld Dreams:
I happen to own an original one from Legends and thought this must be in here! It never disappoints in multiplayer.
Gravestorm:
Nice card draw, oftentimes nobody wants to exile their cards. Evgen if they do - that's also okay and it provides three black.
Infernal Tribute:
I love this card, you can always recycle your stuff or sacrificing something in response to removal or stealing spells (also provides 3). Combos with Gravecrawler.