You can hold a number of blue wonders equal to half your artificer level rounded up. The blue wonders do not count towards your Infused Items count. If you create a new blue wonder while exceeding this limit, you must replace one existing blue wonder of your choice as part of the reaction—a process in which ceruleum from the old device is transferred to the new.

In order to use a blue wonder, you must expend a spell slot of at least half the replicated spell's level, rounded up—the process of energising the ceruleum within. If a spell is a cantrip, you do not need to expend a spell slot to cast it. Only the blue wonder's creator is capable of harnessing its power and casting the replicated spell, and it cannot be transferred into magic items such as a ring of spell storing.

A blue wonder can be used a number of times equal to your Intelligence modifer (minimum of 1). Upon its final use, the ceruleum inside burns out and the item becomes unusable. Over the course of 8 hours, you can spend 25 gp multiplied by the spell's level in raw materials and ceruleum to restore a blue wonder to its full number of uses. A cantrip requires 3 gp multiplied by your artificer level to restore.

A blue wonder is considered its own arcane focus for the purposes of casting a replicated spell: replicated spells do not benefit from the effects of altered arcane focuses (for example the Enhanced Arcane Focus infusion).