The Question was...
How do I make a Solid..... Yes Solid.... Tetrahedron in Revit...?
What is a Tetrahedron?
It's the simplest solid with the least amount of sides (like a pyramid in Egypt)
My first reaction was "just" create it in the massing or adaptive component family editor... simple right?
It turns out it is not possible to create a Solid Terahedron in Revit using any family editor. Why? Because a Solid Tetrahedron requires 4 triangular faces and one rectangular face. You could read more about it here.
So then I thought the best way to do this is to use Dynamo and bring the Dynamo geometry back into Revit. So below is an example on how to create a simple Tetrahedron or pyramid that is 1 unit x 1 unit x 1 unit.
Once you have mastered this concept you could apply this to any sided solid. Good luck polyhedron building and dont forget Dynamo is always Revit's "wingman".