Valenth

Dreamshards are small, specially-processed depleted miracrystals. While counterfeit dreamshards may be purchased from the right people, authentic ones are only distributed by the Silent Rose Organization to its members.

A dreamshard's only obvious purpose is to protect the bearer from the effects of ambient mirajin energy; the processed crystal pulls it away from the person holding it and into itself.
It is unknown if dreamshards have a limit to the energy they can hold or not, or if their use brings any side-effects; the SRO refuses to discuss them in depth with outsiders.