The Otherverse is a small subset of The Other Box which tightly packed together existence-(-2) icosahedra, mentioned in The Other Box article.
Each one of these icosahedra have no existence-(-1) body to neighbour around, as they have been stripped away from them through natural phenomena over very long periods of time. After being stripped, they got pulled inside of the Otherverse through natural forces.
The Otherverse contains an unknown amount of, theorized to be finite, amount of these icosahedra, which are extremely strongly repulsed by each other and are pushing hard against the barrier of the Otherverse, but are unable to get out. If the barrier of this Otherverse were to be broken or busted open, the sudden influx of icosahedra would frantically push around the near existence-(-1) objects, but wouldn't be exactly dangerous.