This is my idea behind the "Schism" video. It's a bit more literal than most of the interpretations I've seen here, in that my idea is more connected to the definition of schism being a religious split.
I believe the contortionists represent gods, or for other purposes, religions themselves. When the female contortionist sinks into the ground and the male appears, it represents one religion becoming two. When the female is making the spiral on the ground with the male's head, I think it relates to the way that some religions borrow ideas (represented by the head) from others.
I also think the smaller beings that are spawned from the vein represent humans. When the creature clings to the female contortionist, it is choosing to believe in that particular religion. After the first one bites onto her, several other follow, perhaps mimicking the spread of the religion.
But the fusion of the two contortionists seems to be the pivotal point in the video. Perhaps the reason the two religions fused is because an alternate religion opposing both of them, somewhat like Satanism opposes all sects of Christianity (which would explain the fireball at the end of the video), has appeared and the two must fuse to face the threat it poses to its own beliefs.
