Arcane Blade

When you cast this spell an ethereal blade forms around the crystal, it takes the shape of a dagger or longsword (your choice), it's damage is 2d8 of the specified damage type below. You are the only creature that can hold this weapon. You are proficient with this weapon, and you may use your spellcasting modifier for attacks.
The damage type of this spell is determined by the color of the crystal you used to cast it;
Red : Fire
White : Cold
Green : Poison
Blue : Lightning