I tend towards aggressive decks on Arena since they are most often the least rare/mythic reliant. I love more control oriented or tempo based decks, but my current Arena position does not allow for me to craft those decks. With that in mind I first looked at the classic red aggro decks that are popular at the dawn of every set (aggro decks tend to do well early on as other decks are not yet refined). I didn't find anything that drew my attention so I looked at white weenie decks and struck out there.
Then I stumbled onto folks playing with Nightmare Shepherd in mono-black decks focused on devotion win condition with Gray Merchant of Asphodel (affectionately known as Gary). The core of the decks seemed to be the Cauldron Familiar/Witch's Oven sacrifice engine from the previous metagame featuring cards such as Ayara, First of Locthwain and Priest of Forgotten Gods to make the sacrifice and recursion of the cats pay off.
This got me thinking about what else would be fun to sacrifice to trigger Nightmare Shepherd and I immediately went looking for "enter the battlefield" effects and that brought me to one of my favorite cards from a previous discard deck; Yarok's Fenlurker. Fenlurker was an upgrade to the previous use of Burgler Rat in discard decks as its an equal effect with an upside. Fenlurkers upside looks even better now with Nightmare Shepherd and the devotion win condition with Gary. A quick glance at various decklists on some websites confirmed I wasn't alone in this thinking.
Looking further I wanted to take the concepts here even further and started to look for other cards that supported the brewing theme around sacrificing and getting things back in return. This brought me to Kaya's Ghostform which I had remembered from a few draft runs where I kept ending up with multiple copies of it. It paid off in a few draft games so I threw it in here to help bring back more fodder for the sacrifice.
I filled the rest of my modest brew in with the curve from other mono-black devotion decks I am seeing online (the fill ins were pretty straight forward black staples; Knight of the Ebon Legion, Murderous Rider, etc).
Here is what I landed on and hope to get around to crafting for Best of 1 play:
3 Priest of Forgotten Gods (RNA) 83
4 Kaya's Ghostform (WAR) 94
4 Knight of the Ebon Legion (M20) 105
3 Yarok's Fenlurker (M20) 123
2 Witch's Cottage (ELD) 249
4 Witch's Oven (ELD) 237
19 Swamp (ELD) 261
3 Ayara, First of Locthwain (ELD) 75
4 Cauldron Familiar (ELD) 81
3 Murderous Rider (ELD) 97
3 Castle Locthwain (ELD) 241
4 Gray Merchant of Asphodel (THB) 99
4 Nightmare Shepherd (THB) 108
Unfortunately it will be a bit of time before I get to play it as I am planning to build my collection via draft and not spend wildcards at this time. We'll see how the meta shapes up and if there is any competitive legs to mono-black devotion sacrifice.