The Shatter is a major event in the life of a being with a split personality. Just before a Shatter, both split personalities decide they can't take coexisting with each other anymore and realize that only one split can have complete control of the host body. They incapacitate the host and proceed to have a war in the mindscape, with only one personality winning. The split that wins gains permanent control and a temporary increase in power known as Apotheosis.
Typically, the more malevolent split gains the edge in a Shatter, although this isn't always the case, as shown with Build and Split. Malevolent splits that die in Shatters are most often sent to Limbo depending on what they did during life. Depending on the power of the host, Shatters can be quite destructive both inside the mindscape and out. In very rare circumstances, the actual body can split in two during a Shatter as well.
There were multiple Shatters during Destroy the Godmodder 2: one between Build and Split, one between Modpack, Alex, and Chaos, a simulated one between Blue and Orange, and one between Omega and Alpha.