Auril's Kiss (5e Equipment)
From D&D Wiki
This flask is filled with a white liquid that turns into a quickly growing block of ice. As an action, you can throw this flask up to 20 feet, shattering it on impact. Make a ranged attack against a creature or object, treating the flask as an improvised weapon. On a hit, the target takes 2d6 cold damage and becomes restrained by growing ice if the creature is Large or smaller. A creature can end this condition by using its action to make a DC 13 Strength check to break the ice. Any fire damage dealt to the ice ends the restrained condition immediately.