Cold Iron

Freezing iron chains lash out wildly from a point you can see. A creature within a 20-foot radius of the point when you cast the spell must make a Dexterity saving throw. On a failure, the creature takes 3d6 cold damage and 3d6 bludgeoning damage, and is restrained. On a success, it takes half as much damage and is not restrained.

A creature restrained by the spell takes 2d6 cold damage at the beginning of their turn. It can use an action to make a Strength check against your Spell Save DC. On a success, it frees itself. If a creature attempts to escape via teleportation or shifting into another plane of existence (such as the Ethereal Plane) via a spell or other effect, the effect fails.

A fey creature restrained by the chains has disadvantage on the check to break free, and has vulnerability to the cold damage it takes at the beginning of its turn. You can forego the damage and instead force the fey to answer a question. It must answer truthfully, though it can be evasive in its answers as long as it is technically within the bounds of truth. After three questions, the fey automatically breaks free of the chains with no check required.