Small variations beyond normal card measurement tolerance can immediately reveal counterfeits
It is much easier to kill in cube than it is in a format like modern, in addition to that it is all too easy to ignore the effect of Keranos in the cube as well
I will be discussing them as part of the 99, if you want to build dedicated commander decks around them, you can also do that, but then their evaluations can shift dramatically both from them being built around completely and consistently available
Ill put some of the highlights in order, then gold, just for people to know what they can expect out of these: Kenrith, the Returned King Akroma's Will Urza, Lord High Artificer Counterspell Cryptic Command Rhystic Study Yawgmoth, Thran Physician Bolas's Citadel K'rrik, Son of Yawgmoth Ragavan, Nimble Pilferer Ancient Copper Dragon Primeval Titan Atraxa, Grand Unifier Tymna the Weaver Isshin, Two Heavens as One Thrasios, Triton Hero #45