This could be a kind of magic of its own, it could be a group of abilities, or only one supernatural skill. Whether it is a special inborn trait, or a simple extension of existing magical talents, another "add-on" for the caster, you decide. Possibly, it could belong to the powers of priests of certain gods.
It is true that something more stays behind after we leave. It is the fuel that powers us, the motives that often stay hidden, yet change the world every day: our emotions.
The basic power is to sense the emotions connected to a location, item or person. While this is a very weak residuum, regular repeating strenghtens it. Also, certain ghosts and ghost-like manifestations are evidence to this fact: they try to do something they did often in life, or perhaps could not achieve, always bound to intense emotions.
Sensing what an individuum is driven with, can be very useful. Of course, for most people it is more than one emotion, and not a few rely on their reason too.
Manipulation is possible to a certain degree, but you must understand a feeling to do so. It could be a simple stating we all know such feelings, or the Game Master could ask for TRUE, intimate knowledge of the given emotion, in its most intense and pure form, bound together with a character's history.
Following are a few examples. No durations, casting times etc. are given. Just know, that these 'spells' take time, sometimes very much time to complete.
Actually senses the emotion of greed, so if you find something, you don't necessarily find anything valuable to you. But sometimes, true treasures can be discovered this way.
"Help of the Hating One"
You convict someone who hates strongly, that his goals and yours are similar enough... and thus gain his help for whatever purpose you have in mind. It is of course very useful to know, what the 'helper' hates.
(It can get dangerous, if the victim finds out, and his hate could turn against you... but sometimes a trusty life-long servant can gained this way. No guarantee.)
The spell gives its caster a feel for things other living intelligent beings do, the more repeated the action is, and the more emotions are associated to it, the stronger. He also feels a weak compulsion to do those things again (but this can be easily resisted). It is merely a feeling, no exact knowledge what to do and what to avoid.
May be useful, may get dangerous.
(Example: At the gates, that smelly guard somehow does not understand your explanation, why you want into the city. Fortunately, you feel a slight itch in your hand and pocket, and pulling out a coin produces a grin on his ugly face...)
Personality of the Emotionalist
The magic is of a slow, manipulative kind, without any cool special effects. It is not a fast and simple way to fame and fortune, not even to power.
While it is definitely possible both to help many, and to do great harm, few are perfect saints or devillish villains. Many are travelers, that seek more knowledge about the world and the people. They are often withdrawn, possibly touchy about certain emotions, and most evade mobs when at all possible.