Morophon is a seven mana colorless Shapeshifter that lets you choose a Creature type when it enters, and then makes all of your spells of that type cost WUBRG less to cast, this only reduces the colored mana you pay, and it even gives those Creatures a +1/+1 boost
While this does tie in with areas of the color pie black excels in, its ramp spells almost always carry a higher mana cost than any other color, making them ill suited for the early game when they are most needed
Its a little pricey, but its also repeatable mill, and thats something you love to see
While we could go for 6 Swamps, 14 Islands, and 16 Mountains and call it a day, we can do a lot better
Insects often have abilities that interact with graveyards, life gain, or sacrifice effects, creating synergy with a variety of game plans
Obviously this gets a lot better with more Xathrid Necromancers