There's a tremendous difference between your rare bomb, like Noxious Gearhulk, and the simply fine Lawless Broker in your deck By playing more than the minimum number of cards, you are reducing your chances, however slightly, of finding your strongest cards as often as possible
I looked for cards that worked well with the deck
Add to that the second most potent card draw engine in Underworld Connections (second only to Jace, Architect of Thought into Sphinxs Revelation) and there are some rich incentives to cast black cards
Kokusho, the Evening Star Draining for 15 every time Kokusho dies is no joke
Finally, a handful of these games - notably the later ones - I'm much less well versed on, so please forgive any errors made in select sections
#1 Kozielk, the Great Distortion Secret Lair Drop Series Market Price: $17.54 Perhaps not much of an accomplishment given you dont see many colorless Commanders at present, but Kozilek, the Great Distortion is the top colorless Commander according to EDHREC, and if built correctly, the Eldrazi titan can be gnarly to play against