Not only do they prevent your permanent from being removed, but they also allow you to point that removal elsewhere
In other words, the player who controls the Opposition Agent whose effect applies (and thus controls the opponent) can choose to give themselves all the play permissions unless they're feeling very generous
That being said, Amethyst already has good access to draw with Friends, Rabbit, Castle, and more
There's also combo of tutoring a creature you want to sacrifice into play
The dividers are back to ink colors but this time with nice art from the set
This can lead to plenty of extra mill over the course of a long game, especially in Commander, where this adds each-opponent mill to any instances of single-target mill