Venoshock

You shoot strands of venom at a creature within range.
Target creature takes 3d8 Poison damage + their level/CR rounded up. Target creature must make a DC 10+your spell modifier Constitution saving throw or become poisoned.

If cast on a poisoned creature, target creature must succeed a DC 10+your spell mod Constitution saving throw or take 6d10 poison damage and take a level of exaustion, or half that on a successful save. 

When cast as a 8th level character, the spell does 5d8 damage instead of 3d8 and 10d10 damage instead of 6d10.