Yawgmoth, Thran Physician is very versatile mono black commander. Yawgmoth is sac outlet, creature removal, card draw and proliferate in a single card. Due to this Yawgmoth is amazing engine piece for several mono black archetypes.
Aristocrat decks are a combination of sacrifice effects, reanimating and value creation. Wincons revolve around multiple triggers, either from dying, ETB or cast triggers.
-1/-1 counters are an opposite of +1/+1 counters. -1/-1 counter decks use -1/-1 counters as a resource and manipulate them for their benefit. Moving, adding and removing the counters on the right moment can turn the tide of the game.
The ways to discard are plenty: cycling, rummaging, end steps discard phase, to name a few. Discard decks are built around triggers from discarding, like madness and synergizes well with reanimating.