You create a long, thin blade of razor-sharp salt crystals. You can wield it as a longsword, using your spellcasting ability to modify your weapon attack rolls. The sword deals 2d8 slashing damage on a hit, and any creature struck by the blade must make a successful Constitution saving throw or be stunned by searing pain until the start of your next turn. Constructs and undead are immune to the blade’s secondary (stun) effect; plants and creatures composed mostly of water, such as water elementals, also take an additional 2d8 necrotic damage if they fail the saving throw. The spell lasts until you stop concentrating on it, the duration expires, or you let go of the blade for any reason.