I know what you mean about the 2 cost but I've sanctioned my 2cost slot for additional kill spells, I again like the devotion of Geralf's Messenger but I can't really are ever adding it as I'm not willing to speed up the deck just to slow it down again :/ In general I find that my devotion is in acceptable condition to facilitate my needs.

Have you thought about adding 1-2 Whip of Erebos? You have tons of life gain with your life link creatures, but this could help as well. Its return from GY ability is useful as well. Not sure what you might replace though. Like the deck!

I appreciate the comment. Personally I feel that the roll that whip would fill is currently filled by Liliana, the Last Hope which proves to consistently offer us more sooner and with less redundancy. I dont feel that the whip can compete with her and as such do not plan to add it to this deck given its current build.

Fulminator Mage to help with the Tron/Valakut matchup? Plus, it adds devotion in a pinch

IAmTheWraith that's what his damping sphere is for.

Nice deck, I'm a huge fan of the obliterator.

After playtesting the deck I now feel like my own needs more arena.

I am happy that you enjoyed the deck, and yes the Damping Spheres act as our additional answer to tron as well as threats like storm. There exists an argument that Fulminator Mage offers us a better alternative to the sphere in our matches vs Tron due to the mages synergy with Liliana, the Last Hope. I however still require a measure to fight storm and as such the dual nature of sphere trumps the mage in value for our sideboard tech.

Damping Sphere is not Modern Legal (according to this site). Fulminator Mage would also help your devotion where the sphere wouldn't.

Sooo Damping Sphere is not modern legal yet because it is a new card coming out in Dominaria. As its a set the we have the spoilers for I dont see a reason in not planing decks to include (or play around) cards that will assuredly be modern staples. I believe that this method of forethought/sight is more realistic for a good deck builder to have.

Upvoted, because black devotion was my first deck in Magic, and seeing it scaled to a competitive level in a format like Modern is always a way to make me happy.

Also because the deck itself is actually good, with Phyrexian Obliterator, Gatekeeper of Malakir, etc.

Have you considered Temporal Extortion? It's quite good, but almost unplayable in anything but mono-black.

I know of the card however I do believe it is unplayable in modern. The primary reason why is because that card acts as a non recurable, harder to cast Merchant. We can assume that we will never be given the extra turn so the value of that card will often be as a 4 mana spell that on average deals 5-7 damage to our opponent. I do not believe that the addition of this card would be worth while because it is so limited in nature.

Are you thinking about replacing victim of the night with cast down when it comes out?

Josu Vess, Lich Knight might be a worthy include. You have enough potential mana and would get a great finisher for your deck.

@LordDerrien I already have a finisher in the form of Gray Merchant of Asphodel and he is much more consistent than the Lich king.

@Fablab I have thought of adding Cast Down but Im unsure of its consistency. You see Victim of the night fails to hit very few major threats that show up in modern competitive. Notably Cast Down does.

Is walk the plank worse or better than victim of the night?

The way I value instant speed spot removal is in its ability to disrupt combos. I consider Walk the Plank to be a good removal card, however Tribal merfolk decks do see competitive play and spit second removal of Merrow vs those decks is key.