Unnamed Combination Potion

After drinking this potion, for a duration of 8 hours, you gain a bonus +1 to Constitution for the duration. Additionally, you gain 20 to your maximum HP for the duration. While under the affects of this potion you have resistance to necrotic but are vulnerable to poison damage as the potency of this blend has made it a little toxic in and of itself.

The toxicity of the potion continually tests the person who drank it, and over the duration of the potion's effects, the one who drank it must make a number of DC 15 Constitution saving throws, taking 4d6 poison damage on each failure, or half as much damage on each success.