I've just tried my first run with the new DLC of Binding of Isaac: Afterbirth, and I've found several new items.
One of them is this Devil item:
It's called Multidimensional Baby and it costs 1 heart container.
It's a familiar that follows Isaac and it rarely shoots a new kind of tear.
I say "rarely" because it doesn't shoot with the frequency as my other familiar (Little Steven).
It's a blinking black/white tear, what's its effect?
Best Answer
The Multidimensional Baby item is described in this video:
As shown in the video, the Multidimensional Baby familiar doubles the projectiles you and your other helpers fire, along with giving them the flashing black and white effect. Contrary to what's said in the video, you don't necessarily need to be in contact with the familiar to make this effect work. While that's one way to get the effect, any projectiles that pass through the familiar will also gain this effect. The Multidimensional Baby will follow your movements, but with a delay of a few seconds, making it difficult to use if you need to move around a lot.
Other than doubling the number of projectiles you fire, it doesn't add any special effects onto them.