Pentachoron

A triangle becomes a tetrahedron (a type of pyramid), then a pentachoron (a hyperpyramid).

Geometrically, K₃ relates to a triangle, K₄ a tetrahedron, K₅ a pentachoron, etc.

The tetrahedron is a 3-simplex whose 4-simplex analog is the pentachoron, a four-dimensional body which can be orphographically ^([sic]) projected onto a quincrux (as well as a pentagram and other shapes).