For Envy then I suggest a magic item that is in a very difficult trap that if you fail to disarm will destroy the artifact.
For the double down make it something that if multiple people work together on they could do it rather easier, but it will result in a lesser very for each of them instead of the one big version.
An example is a Fountain that if one person drinks from he gets a +X (whatever you are comfortable with) inherent bonus to Con, but if multiple people drink from it they get a +1 inherent bonus to COn. However the trap they have to get past first will drop a big rock into the fountain and destroy it. The trap is one of weight distribution on multiple tiles at the tame time. Thus multiple people can cover all the tiles at once easier rather than one person trying to do so. Make it a one way passage that loops back around so if you are going to try you have to try now.