While yes, the Street Fighter Secret Lair is interesting and fun, their abilities seem very clunky for a deck like Sisay
Im a fan of protection spells that leave your board stronger than they were before the effect you needed protection from, and thats exactly the Mutational Advantage youre getting
Explore fully resolves first and you draw a card, perhaps a land you'll play later
Free-for-All In a similar way to #8 Gerrymandering above, this enchantment is a cool way to set aside all of those nasty creatures, and then slowly, over time, dole them out randomly under peoples control as they take each of their turns
Historically I have always kept my gold cards to an absolute minimum in the cube
Unholy Annex / Ritual Chamber Unholy Annex is a new Phyrexian Arena that you have to pay 1 more life for, so hows this room enchantment better than the original black enchantment