I would advise against it.Multi-accounts are systematically disadvantaged here when they are merged.
For example, for the following reason:
Unless otherwise noted, purchase limits are per DomiNationsWorld account, not per DomiNations Base.
In the early days, this was true for the cheap estates.
Currently, it affects this
Double your rewards by logging into DomiNations World and collecting Legendary Recruitments and Crowns!
and the rewards from the new world trivia ticket shop.
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If you still want to do it, support will help you. However, you will have to prove that the accounts belong to you, e.g., by providing invoices, the location/time where the account was created, etc. – they will guide you through the process.