I'm putting together a cube comprised of all the most complicated cards in the history of Magic.
So far I'm determining complexity solely by length of Oracle text.
I have a ruby program that I use to do a bunch of magic things. So for this I just asked it for:
* The 40 creatures in each color that are the most complicated.
* The 30 non-land, non-creature cards in each color that are the most complicated.
* The 30 (each) artifacts and lands that are the most complicated.
That's 384 cards (410 cards minus duplicates that show up in more than one color). It seems like a cube has a minimum of 3 x 15 x 8 = 360 cards so that's a good starting point.
There's currently no consideration of either mana fixing or mana curve. And plenty of the cards need either removing or having more support cards added (example: Higure of the Still Wind).
You can see the cards in this visual spoiler