Wondrous item, rare
This ethereal thread binds two fates together. When you touch a creature (this can be part of another action), you attach the string to both yourself and the target. While bound, whenever either of you gains a beneficial effect from an external source—such as a spell, potion, or similar magic—you can choose to share the effect with the other.
The string breaks after sharing three effects or if one hour has passed since attachment.