The Ivory Dessert

You are presented with a selection of fancy cakes arranged in a silver box. These cakes are sprinkled with some kind of granulated substance, which is a different color when viewed at different angles. Is it... sugar? They are presented with a note that says, simply, "Eat Me." 

A creature that partakes of the dessert gains some special benefits.  The creature gains the benefits of a long rest (all hit points regained, all spell slots restored, hit dice regained). A creature under the effects of these fancy cakes makes all Wisdom saving throws with advantage.  These benefits last for 12 hours. Whenever a creature under these effects makes an attack roll or a saving throw before the spell ends, the target can roll a d8 and add the number rolled to the attack roll or saving throw. Its hit point maximum also increases by 2d10, and it gains the same number of hit points. These benefits last for 12 hours.