This is 5-Cell (pentachoron, 4-simplex), four-dimensional object bounded by 5 tetrahedral cells It is also known as the pentachoron, pentatope, or hyperpyramid. It is a 4-simplex, the simplest possible convex regular 4-polytope (four-dimensional analogue of a polyhedron), and is analogous to the tetrahedron in three dimensions and the trianglen in two dimensions.

I made it in classic MC with the help of Mrmonkey91 by hand. No models were used in the making. Then I copied it to Beta MC because the lighting is much better. The original is in Classic MC server: Opticraft Dev Server.

(Used library: Wikipedia en.wikipedia.org/wiki/5-cell)