Accursed Crystals

You point, and a line of crystals grow from the ground in a 5' by 60' line. Any creatures in the line must make a Constitution saving throw as a sickening light radiates from the crystals. If they fail the save, they take 6d6 necrotic damage and are Poisoned for the duration. If they succeed, they take half as much damage and are not Poisoned. A Poisoned target may repeat this saving throw at the end of each of its turns, ending the effect on itself on a success. For each turn you maintain concentration, you suffer 1d4 poison damage (Increases by 1d4 per 2 rounds), which can not be reduced in any manner, to build up a charge within the crystals. Every 2 rounds, starting at 2d6, your crystals glow brighter, and will gain an extra 2d6 necrotic damage, maximum of 8d6. When you end concentration, or the spell ends, the crystals detonate, and all creatures within 5 feet must make Dexterity saving throws, or suffer the damage the total damage of the build up.