Parenting lights to monsters

[Romulator]

I think you're best to just duplicate the entity and then edit it in the Model Editor. In the Model Editor, you can attach the billboard and light directly to the body or bone of the entity so that it moves with the entity. The Model Editor does allow you to place lights and billboards as the are.

I recommend looking at other entities if you have to, to see how they attached their billboards/lights. I believe the Construct enemy has both billboards and lights attached to it.