Today, Adam Styborski unveiled Void Winnower, a slightly odd creature, even for an Eldrazi.
What makes it so odd is that its text contains the word "even," waters Magic doesn't typically dip its toes into. A Gatherer search for "odd" and "even" (when ignoring things like Veiling Oddity and Demigod of Revenge) yields very few results. In fact, prior to Void Winnower, only three such cards existed.
In the case of the Chaos twins, there are no Multiverse (our internal database) comments to look back on for guidance as to the purpose of the even/odd dichotomy—but they were clearly designed to be wacky on/off cards that players would fight over based on the state of the battlefield. Granted, constantly counting the number of permanents on the battlefield is a bit trying, so you can imagine why this mechanic was never repeated.
Ashling's Prerogative, however, we have a bit more insight into. The comments in Multiverse were as such:
JT 11/20: Seems fun!
DAL 11/29: I like it!
PB 1/5: Fantastic!
MJ 1/5: Hope tokens don't generate too much confusion. In any case, it is a nice card. :)
Del 1/29: Tokens and animated lands, you mean. The card may have other issues.
You can see that there was some concern over the confusion cards with zero or nonexistent converted mana costs could cause, which is why Void Winnower clarifies that zero is even in its reminder text.
So what's going on with Void Winnower? Why is it so . . . odd? I think this bit from the art description sums it up nicely:
Mood: The will of the Eldrazi overrides everything, even the laws of physics.
The description also says that this particular Eldrazi "projects a weird aura of silence and stillness, nullifying even gravity."
Which you can see clearly in the art:
Void Winnower | Art by Chase Stone
Now isn't that odd?