There are two objects, one convex and one nonconvex, that can both be called regular icosahedra. Each has 30 edges and 20 equilateral triangle faces with five meeting at each of its twelve vertices.
The Absolute Icosahedron is actually not made out of Absolute Pentagon's, it is actually made of Berry Triangular Prismatic Containers, which are pretty much absolute pentagons but in triangle form. This verse constantly is moving and is the fastest moving absolute shape in all of existence, as it is constantly reforming itself. This, however, means it is very easy to escape, as holes are always put into the icosahedron whenever it moves. It spins once every 1 Voidsecond. The reason why it shapeshifts is because it needs to constantly expand and add any shapes that are a part of the absolute chain into it, even if it's bigger than this shape.