Probably bad item idea
(Merchant)'s Last Wish- (Type)
Ever wanted a more endgame item than the Life sized gingerbread house, well behold upon the last wishes, requiring a whopping 100'000 stomach capacity for a charachter to even eat but in return providing 1'000'000'000 calories, there would be variants to this item for buffing body parts, you can only get them from a new NPC who sells them for a stupid price (High or low depending on what the dev wants) what makes the last wishes hard to use is the following,
1. you can only have one copy of a type of last wish at a time, 2. they only have 1 type of last wish in stock per day.
I guess that a last wish acts as this games "Final Boss", or at least one that does not rely on gain speed.