Ambush Shard(partial credit to dandwiki)

A small rift appears behind a target within range and shoots a semi-invisible glintstone shard at it. Make a ranged spell attack against that creature with advantage. On a hit, that creature takes 1d12 force damage plus 1d12 piercing damage. This spell scores a critical hit on a roll of 19-20.

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d12(your choice of which damage type increases) for each slot level above 2nd.