The caster of this spell prepared a vial of water to hold a different spell, effectively creating a temporary potion without having to undertake all of the regular preparatory work needed to create a potion.
While holding a vial of water, the caster would first cast Darsson's potion followed by another spell directed at the vial. The second spell was absorbed into the vial and stored for later use when the water from the vial was imbibed. Only spells of low to mid-range power could be stored in this manner. Additionally, only spells that one would cast upon themselves for beneficial results could be stored.
An interesting note with this spell is that the follow-up spell need not be cast by the caster of Darsson's potion, meaning that a more powerful wizard could cast the spell into the vial and someone of weaker power could use the stronger stored spell.
In addition to verbal and somatic components, this spell required a vial of water to cast.