Bepsi's Hell Spear

You summon a burning incorporeal spear and launch it towards a target within range. Make a ranged spell attack against that target. If there are any creatures within 15 feet directly behind the target and the attack roll would also hit them, they are also hit. On a hit, the first creature takes 2d10 piercing and 3d8 fire damage, and all creatures after the first take 3d8 fire damage.

In addition, the orginial target's speed is halved until the end of your next turn.

At Higher Levels.  When cast using a spell slot of 4th-level or higher, the spell deals an additional 1d8 fire damage to all targets per spell slot level above 3rd.