The easiest elementals to summon and control are fairly small; they are often called the Wildfolk in places where they can manifest spontaneously in physical reality. They are usually only visible to magicians who use Summoning magicks or people with the second sight. (Stolen from Katharine Kerr’s Deverry books.) For summoning purposes, they qualify as lesser spirits. Gnomes are minor elementals of Earth, usually manifesting as humanoids one to two feet tall, and their skin is colored in earth tones. Sylphs are winged humanoids that usually range from six inches to a foot in height, and could be mistaken for pixies (a nature spirit) and sprites (a player-character race) if the observer could not note the hues of their skin and hair: all the colors of the weather, blue, white and grey. Salamanders are less human in appearance, looking like some sort of hybrid between an actual salamander and a human. They tend to be mottled or striped with black and the reddish-orange of live coals, and usually range from three to six inches long. Undines are translucent blue and green humanoids with varying fishy characteristics.
The more powerful elementals are usually discussed by their elements. Air elementals usually manifest as a cloud or whirlwind with eyes; fire elementals as a leaping flame with a hint of a face, water elementals as a wave that turns its curl in the direction of its attention, and earth elementals as crude humanoid figures or sometimes flowing blobs of earth or rock with pits where the eyes are located.
The elemental realms, while infinite, do have borderlands where they meet. Beings that hail from these borderlands are generally less powerful than those that draw from unalloyed elemental power, but have their uses. Fire and earth make lava, fire and water make steam, fire and air make heat, earth and water make mud, earth and air make dust (sandblasting attacks), water and air make mist; fire, air, and earth make ash (think pyroclastic flow here!); fire, air, and water superheated steam; fire, earth, and water boiling mud; earth, air, and water a sort of muddy rain. Reduce a wizard’s Sorcery AV by 2 when summoning para-elementals.
Djinn are elemental creatures whose veins flow with fire instead of blood; when mortally wounded, they become a living pyre. Their classes, in descending order of rank, are the Marid, the Afreet (highly intelligent), the Sheitan, the Ghillan (shapeshifters that always have asses’ hooves), and the Jann.
In China, the four elements were represented by the Lung (a dragon, representing air), Fêng-Huang (phoenix, representing fire), Qi-Lin (unicorn-like beast with the body of a stag, hooves of a horse, and head of a dragon, representing earth), and Pi-Hsi (a tortoise, representing water). Some elemental spirits may resemble these creatures, just to add to the confusion of taxonomists.
Earth whales are creatures of elemental earth that swim through the ground and spout geysers when they surface.
Messenger spirits are minor sylphs that hail from the Great Library in the Cumulus Citadel on the Elemental Plane of Air; they work for (named) Librarian spirits. (AV 5.) They can usually be bribed with a pamphlet they haven’t read or a song they’ve never heard before. Their cousins, the scentstalkers, are superb trackers by scent and hail from Evanescent Garden in the Cirrus Palace; they can be bribed with rare perfumes. (AV 7.)
Guide salamanders are normally found in the Sixfold Labyrinth beneath the City of Brass on the Elemental Plane of Fire. They have a superb memory for paths and can unfailingly guide a person along any path they have traversed before... as long as the landscape isn’t shifting. These simple creatures will usually show up for highly purified lamp oil or other such quality flammables. (AV 7.) Torch salamanders are often conjured to provide light without maintaining concentration on fire magicks, and will work even for good quality coke or charcoal. (AV 3.)
Porter gnomes are unusually large for a lesser elemental, and quite strong for their size; they are very slow, but can carry impressive loads and have enough wit to stack bricks to build walls. (AV 8.) Mouth gnomes have been pressed into service many times as door guardians: they are about eight feet in diameter, but in their native habitat they are effectively filter feeders. As door guardians, they form a short corridor that can devour anyone who goes through without authorization, and are quite hard to break through. (AV 12.)
Current undines are small but pack a great deal of power over the flow of water: they can propel a small boat or hold back several hundred gallons of water from spilling out of their container. (AV 9.)
In places of power, a nature spirit may decide to take on a regular manifestation. A nymph is a spirit of the land, an alseid of a grove, a naiad a spirit of a streams, fountains, and brooks, potamid of a river, and a nereid a spirit of the sea. (If you can tell the difference between a sea and an ocean, a spirit of the ocean is an oceanid.) Oreads claim the mountains and grottoes, a napaea (pl. napaeae) watches over a mountain vale, and an auloniad a pasture. A dryad is a spirit of a forest, whose existence is tied to that of the forest; hamadryads are lesser beings that are tied to individual trees.
Nature spirits with independent manifestations are usually dangerous. The lonely ones will simply keep someone around for good company and not let them leave; the ones with nastier attitudes will lure victims to their doom for fun or as a preventative measure against those who fail to show the proper respect for the balance of nature. Rangers are much in demand for treks through the wilderness to keep the unknowing folk from doing things that will attract the attention of the local nature spirits.
Nature spirits are found both in their local places of power, in which case they can be summoned by those who wield the power of Ecos, and in the transcendent plane, where they can be pulled up by those who wield the power of Nature. The greater the difference between the local environment and the place of the spirit, the harder the summoning gets. Pulling up a volcano spirit in the middle of a forest is usually a –3 penalty, but a wielder of Ecos can’t get one at all if there aren’t any volcanoes on an island!
In places where civilization has drastically affected the local balance of nature, such as extensive farmland or large cities, the local spirits are quite different, and generally a bit harder to conjure than regular nature spirits because of the turbulent nature of human-modified ecosystems.
Hungry ghosts should be dangerous... a larva (pl. larvae) is a malevolent ghost, also known a lemures, while manes are generally good-natured.
Demons are the denizens of an outer plane.
Angels follow the classical definition: messengers. They are servitors of some deity.