This is a 100% OpenSCAD rendered chess set. No importing of any other files necessary.
The Knight was though most difficult to design, but I like how it came out.
Note that OpenSCAD 2016+ is needed for some advanced sweeping for the Knight's mohawk and the Rooks top bricks. It should gracefully degrade if you do not have a version of OpenSCAD that supports angled rotate_extrude.