Blackened Heart

You reach out towards a living creature that you can see. The target must make a Constitution saving throw. If it fails, its body is filled with vile poison, and it takes [roll]10d6[/roll] poison damage at the start of its next turn. If the target is reduced to 0 hit points before the start of its next turn, the poison explodes outward from it in a shower of disgusting bile. Creatures in a 10-foot radius of the target must make a Dexterity saving throw. If they fail, they take [roll]10d6[/roll] poison damage, or half as much on a successful save.