Physical Appearance
Poltergeists appear invisbilie to the normal eye and when visible their whole body appear but translucide. They do have clothes on that don't appear translucide unlike Apparitions..
In most cases Poltergeists are teenagers, young adults, adults, or elderly person's ghosts. Elderly person's are rarer because life expectancy is longer and therefore old age deaths usually involve no regrets. Children cannot become Poltergeist for the simple reason that they become Spooks.
Ecology
To reach peace, a Poltergeist needs to either free itself from this regret by achieving what they could not do before their death, or to overcome this regret. In almost all cases where an elderly person becomes a Poltergeist, it is to stay with their loved one in order to wait for them.
If a Poltergeist succomb to their regrets or give up on them. Then there would be no comeback and they become Shades.
Diet
Being Ghosts, Poltergeists do not need to eat in order to survive.
Habitat
Poltergeists can be found in any type of environment but they tend to regroup and live in or near populated towns. There is however some haunted towns that are populated with mostly Poltergeists like Ormir in Gallia.
Rarity
Common
Behavior
Poltergeist mostly behave just like any normal living person. They tend to live among people, these being either their living loved one, around other ghosts, other Poltergeists or just living people in general.
They can become a threat if upset, angry or attacked but they generally stay quite calm. It is worth noting that Poltergeists are still ghost of previously living people and they keep their own personality so this has a huge influence on their behavior.
Threat level
★ ★ ☆ ☆ ☆ ☆ - Docile: Poltergeists mostly have a quite peaceful behavior and "live" their life as they want, trying to eventually get rid of their regrets. However, as every beings, they can also get upset, angry at people and tries to hurt them. Since they have a very good ability to interact with the world of the living, they can hurt people by throwing objects and sometimes even push the livings. You better be nice with people and especially with the dead ones.
Abilities
Poltergeists have a better ability to interact with the world of the living. They can move objects much more easily than other Ghosts and make noises.
Magic
It is known that the type of magic that allows Poltergeist to manipulate different things of the world of the living is the Spirit elemental magic. However, it is unkown why they keep this ammount of inner mana after their death.
The most common spell used by Poltergeists is telekinesis. They tend to use this magic to move objects more than their own force.
Use
Poltergeists have no use in any spells or rituals. It is however possible for Wiccans to invoke them through a ritual of Unbound Creature Invocation. The fact that it is unbound means that the Poltergeist will have either no obligation to show up or no intent to cooperate with the Wiccan. In some cases, the Poltergeist can feel attacked and can try to hurt the Wiccan as a defense mecanism.
There are many reasons that a Wiccan can try to invoke a Poltergeist but the main reasons are: in a Rituals & Incantation class for Wiccan students, in a spiritualism way to communicate with a loved one or to get informations from the ghosts in a Knight case.
History
Many people discuss the realtion between Phantoms and Wiccan's familiars. Some people even think that Phantom may be the first stage of becoming a Familiar. Yet, many writings reject this hypothesis through the simple fact that Phantoms and Familiars comes from different dimensions, one being the Spirit Dimension and the other being the Familiar Dimension. Another fact that goes against this hypothesis is the extreme diversity of the Familiars while the rarity of the fauna isn't that balanced. Therefore, many consider this hypothesis as refuted.