Enchantment
Whenever you cast a spell that targets only a single artifact or creature you control, create a token that's a copy of that artifact or creature, except it's not legendary.
The triggered ability of Vesuvan Duplimancy triggers only if you cast a spell that targets a single artifact or a single creature and nothing else. The ability will resolve before the spell that caused it to trigger, and a token will be created even if the spell you cast was countered or permanent it was targeting is now an illegal target.