Introduction - If you have any usage issues, please Google them yourself
When started with the parameter /slave, VSTHost goes into Slave Mode and waits for a Master to control it. The first (and currently only) master is a VST(i) plugin that can be embedded into any VST Host program (even another instance of VSTHost), called Legree. It comes as an effect and as a VSTi, since there are hosts that accept only effects, hosts that only accept VSTis, and of course hosts that accept both.