Evoker's Blade

You transform a melee weapon you're holding into an elemental blade.  For the spell's duration, the weapon uses your spellcasting modifier for attack and damage rolls.  In addition, choose a damage type: fire, cold, lightning, acid, poison, force, necrotic, or radiant.  The weapon's damage type changes to the chosen type.

At 5th level, Evoker's blade ignores resistance to the chosen damage type. At 11th level, Evoker's Blade deals half damage against creatures with immunity to the chosen damage type. At 17th level, Evoker's blade ignores immunity to the chosen damage type.