Echo Blade

You conjure a spectral, shimmering longsword made of pure sound in your hand. While holding the echo blade, you can make an attack with it as an action. This attack has a reach of 5 feet, and uses your spell attack modifier. An attack deals 4d8 thunder damage on a hit. 

At higher levels: When you cast this spell using a spell slot of 5th level of higher, you deal an extra d8 of damage per spell level. When you cast this spell using a spell slot of 7th level or higher, you gain advantage on concentration saving throws.