The patience is the mono-black grind, winning the long game instead of the fast one
Cursed Mirror Rating: 3/10 As far as mana rocks go, one that gets to attack as a (hopefully) big creature on the turn you play it is probably pretty good
These have all held their price points fairly well given their relevance in Standard and Commander--they come into play untapped and are fairly easy to "turn on" so that they can tap for both colors of mana
Im not a believer in proliferate as a reasonable way to build around energy, so Im very skeptical even of the best proliferate cards, including Atraxa, Praetors' Voice, even though Atraxa seems to have been the most popular energy commander until recently
Reconstructed mainly around cards from Base Set, Jungle, Fossil, Team Rocket, and others, it is also known for its characteristic Reverse Foil
For 3 mana there's better things to be doing