Nykthos, Shrine to Nyx

Cantrips are spells with a draw effect on them. Cantrip decks are often instant and sorcery spell slinger decks and aim to cast as many cantrips as possible and creating value from the cast triggers.

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.

Combo decks are control heavy decks, running a heavy amount of card draw or tutors. If the decks get to assemble the combo pieces the game often ends in an infinite combo.

Burn is reds primary mechanics. Red can deal massive amounts of damage to single target or deal multiple amounts of single damage to multiple targets. Burn decks aim to win with massive outbursts of big, uncounterable and unpreventable damage to opponents (and sometimes the burn player itself).

Lifegain is one of the the most popular themes in EDH. Multiple triggers to gain life and value received from the lifegain triggers are really fun to follow as a player. Often lifegain is combined with another theme, +1/+1 counters or creature tokens, as pure lifegain is often not powerful enough to win the game.

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.