I'm running a game where elves don't have souls. We've established, though, that they can take souls from the dead, and that this is a big deal for them culturally. My request would be what perks and responsibilities should come with being the only elf in town with a soul? And what sort of minor gameplay perks could this translate to?
Two takes on soulless elves depending on how elves might view other people:
People live sad lives:
The soulless elves have an undeniable sympathy for the short lives of those around them. Elves, being immortal, have no need for souls. Unlike the short-lived people of the world, the elves have no need to pass on to an afterworld and so were never gifted with souls.
Instead, they have chosen to use this void to help resolve the wrongs and regrets of the deceased. By accepting the soul of another into their own body, they become aware of their desires, concerns, and failures of that person. The elf then takes these facts and seeks to resolve them to the best of their ability. They will attempt to romance lost loves, amend their misdeeds, help their friends and family left behind, etc.
In society, the elf is expected to follow through on these deeds and do whatever they can to help the troubled soul. As long as they do so, other elves will attempt to help them on the quest. They will provide free room and board (or at least discounted) and will attempt to lend travel supplies.
Failing or neglecting these responsibilities, however, may lead to every elf nagging you to no end in being such a dick to the poor soul you brought into your body.
People are books:
The soulless elves harvest the souls of those long dead for knowledge and clarity. Resurrecting these souls allows the elf to venture back into their lives during meditation, allowing the elf to relive history from their perspective.
An elf rooting through the former life of their adopted soul
In this situation, when the elves meditate, they can experience an equivalent amount of non-consecutive time in the life of the soul inhabiting their body. This may provide vital information for current circumstances and adventures, or it may provide valuable historic information that can be traded to others, elf and non-elf alike.
However, this fact about elves is widely known amongst the world. People may attempt to bribe or force you into accepting a soul to reveal hidden knowledge to them (for good or ill).