Hi

When the campaign changes from bronze to silver do all the monsters automaticaly upgrade to silver level or can you have bronze monsters i a gold level?

In other words, do the overloard allways have to upgrade his monsters?

Yes, the OL must always spend the Conquest if he wants to upgrade his monsters.

The campaign level simply determines how many he can upgrade to which level.

At copper he can only have one set of monsters at silver. All others will remain at copper.

At silver he may only have one set of monsters at gold. All others may be upgraded to silver.

At gold he may only have one set of monsters at diamond(?). All others may be upgraded to gold.

Hope that helps.

+1 for Dragon's answer. The OL does indeed need to spend the CT to get the benefits of all monsters being higher "level."

That´s not 100% accurate. Lieutenants, Sharks and Tentacles automatically upgrade when the campaign level changes.

Of course that won´t save an OL from being slaughtered if he doesn´t upgrade other monster types as written above as well.