Thunderbolt Knife

You create a shard of pure lightning and fling it at one creature within range. Make a ranged spell attack against the target. On a hit, the target takes 1d8 Lightning damage plus your spell casting modifier . Hit or miss, the shard then explodes in a massive crack of thunder. The target and each creature within 5 feet of it must succeed on a Dexterity saving throw or take 1d8 Thunder damage.  The spell emits a thunderous boom audible out to 300 feet when the shard explodes.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the Thunder damage increases by 1d8 for each slot level above 1st.