Opalescence also can turn all enchantments into creatures, allowing you to create an army of buffed Background creatures
The reason isn't quite as clear-cut as most examples, and winning gets you the Bad Ending
It is not trying to impress Instagram
Dark Ritual effects one-shot bursts like Dark Ritual, Cabal Ritual, and Songs of the Damned for explosive early plays Swamp-scaling engines Cabal Coffers, Crypt Ghast, and Nirkana Revenant multiply mana based on your Swamp count Life-to-mana conversion K'rrik, Son of Yawgmoth and Bolas's Citadel let you spend life instead of mana Sacrifice-based mana Phyrexian Altar and Ashnod's Altar convert creatures into mana for combo turns Treasure generation Revel in Riches, Black Market Connections, and Pitiless Plunderer produce Treasures tied to death triggers Building a Black Ramp Package Mono-black ramp packages should be built around the Coffers engine: Cabal Coffers, Urborg, and 2-3 Swamp-scaling payoffs like Crypt Ghast and Magus of the Coffers
RDW is all about redundancy, everything is doing damage and everything is pretty direct
Creatures are a big part of that plan