How do I add and delete units from a nation?

[Endoperez]

Originally Posted by Epaminondas

Also, is there a 3-unit limit on the # units/commanders a magic site can hold? If I try to put more than 3, I seem to get an error.

A site can only have up to five features. Generating X gems of type Y is a feature, allowing the recruitment of a creature is another. That's how Edi's suggestion "clears" a site - the existing features are replaced.

Your site probably generates two types of gems, so only three additional units fit.