Mono Black
Black is the colour of death, cunning, selfishness, undead and terror. Black can do almost everything the other colors can do by paying life. As black can do almost everything, it is extremely popular color and has a multitude of very different, unique commanders.
Mono Black themes
Reanimate
Reanimate decks brings back creatures from the graveyard straight to the battlefield. The reanimated creatures are often expensive to cast, like demons, and are complete haymakers compared to the reanimation costs.
Zombie tribal
Zombies are first and foremost: black creatures. Mono black is the original zombie tribal colours, and later received multiple great cards in Dimir colors.
With mono black zombie tribals are fully combat focused decks with resource advantage from abusing the graveyard. With looting effects, discard and creatures dying the graveyard is zombie decks most valuable resource after the zombies on the battlefield.
Vampire tribal
Vampire tribal is second most popular mono black tribal. Eternal vampire have a multitude of different commanders available and different game plans, too. One vampire tribal can focus on full combat with lord effects, other focusing on life gain and life loss and third can focus on stealing other players creatures.
Discard
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.