Cursed Flame

Seeds of necrotic fire spread through and area and growing with each passing moment, originating from 3 squares within range. Each creature in an affected square must make a Constitution saving throw. On a failed save, a creature takes 2d6 fire damage and 2d6 necrotic damage, or half as much damage on a successful one.

The necrotic fire lingers in the area for the spell's duration. Any creature that enters or ends it's turn in the affected area must make a Constitution saving throw, and suffer the same effects.

Additionally, For each turn the spell remains active, at the beginning of the your turn, choose a square adjacent to one of the affected squares. It also becomes affected by the spell.

At Higher Levels:

When you cast this spell using a 6th spell slot or higher, the fire and necrotic damage increases by 1d6 for each slot level above 5th. Additionally, for each slot level above 5th, add 1 to the number of squares the spell originates from