You can open the Mercury client from any device.
So you can share the same WhatsApp number and account on multiple devices.
When you pair a phone number with a Mercury client, it opens the chat tab on your PC (or other device you're using).
If you want to open the same client with the same chat on another PC, simply log in to your Mercury account on that PC and open the same client. In this way you have WhatsApp chat open on two devices simultaneously.
You can do the same operation on as many devices as you want and you'll keep the same number active on different devices without losing synchronization, contrary to what happens when you connect to the traditional Web WhatsApp.