Seething Blackness (Standard)

Controlly almost-mono-black, with several angles going on:

• Discard to disrupt midgame and trigger Shrieking Affliction.
• Devotion to secure several large Gray Merchants.
• Hythonia(s) for a late-game selective creature wipe.

With the main one being devotion, there's a greater proportion of permanents than there might otherwise be. Nykthos can greatly hasten the Gorgonian monstrosity abilities, and with a Keepsake Gorgon or two, can lead to a pretty fearsome group remaining after the wipe.

Returned Phalanx and Desecration Demon perform a similar role to one another: cost-effective and mainly defensive creatures to raise devotion levels in the early- to mid-game. The Desecration Demon in particular can usually force a response of some kind.

The ideal Mind Rot is the turn three or four (sometimes five) one, when the opponent has exactly two cards in hand. They would have thought themselves mostly safe from the preceding or subsequent Shrieking Affliction, which itself serves devotion and stacks rather pleasantly.

By the time devotion is at 5 or so, the Gray Merchants can land some pretty heavy hits, and the resulting life increase means you can take some more damage without having to give up blocking creatures or the devotion they maintain.

Still needs tweaking and streamlining, but that's the basic idea.