Animate many identical rigs at once

Hi, this is my problem:
I have twenty identical characters with their own duplicates armatures. I’m trying that all move at once.
I could animate the characters one by one, but would save time if there is another way to do it.
Can I create a “master” that control all the armatures?

AFAIK, several armatures can share the same action. Animate one armature, switch the dopesheet to be an action editor, there in the header is that name of the action for the current armature. Select the next armature and in pose mode, look to the action editor. In the field where the action name is, click on it and select the same action as the first armature. Rinse and repeat as needed.