Elixir of Viper's Vexing

A minute after drinking this elixir and for the next 8 hours, you gain Immunity to Poison damage, to the Poisoned condition and to contracting diseases. At the end of the duration, if you avoided any Poison damage or the Poisoned condition while under the elixir's effects, you must succeed on a DC 15 Constitution saving throw or become Poisoned until you finish a Long Rest. Dark sediment gathers at the bottom of the milky-colored liquid in this vial.