One notable omission from this list is [[The Soul Stone]] blacks best mana rock
But if youre looking for a deck that can quickly and easily be upgraded to fit into a competitive environment, Id probably go for Elven Council
I won't go deep into each one, but they all have some form of cycling which can be a boon if drawn later in the game when you don't need them, or, of course, for cycling strategies (toss in a Fluctuator and burn through your whole deck.) Some produce colorless or single-color mana
Being a group image, there is much more of the light blue on this otherwise sepia card, with all characters benefiting from the Sapphire ink outline
Special thanks are due to interviewee Jeremy Jarvis
I dont think itll stir up too much trouble in Standard, but it may prove an effective hatebears or aggro commander in EDH