Instead of releasing a glut of new Historic cards into MTG Arena this November, Wizards appears to be pacing things out more, and instead of doing it as a paid content addition, Wizards has announced it will be examining how to introduce these cards currently
The aim of Maze of Millennia is to bring classic anime cards to life and finally introduce those which have a chance to gain a competitive edge in the current metagame
When you cast it you can pick which half you want to start with, and later you can unlock the other half by paying that halfs mana value
Just make sure you bring your magnifying glass with you
This is a powerful Yawgmoth's Will, one of the most powerful cards ever printed and so powerful and nasty that it's restricted in Vintage and banned in most other formats (but not Commander, oddly enough)
Thankfully, we've just learned a whole lot more about the upcoming MTG Final Fantasy Universes Beyond set thanks to this flood of great spoilers