I'm bumping this thread, even though it's admittedly ancient, so that I can post and update new entities and beings I'm adding to my mod, without crowding my other ongoing mods, particularly as I still reference this mod, and plan on using, or atleast updating and/or somehow incorporating, the information herein.
Here's what I'm planning, first off:
Six small elven entities, four of which will be interdependant on one another, and which will each operate during a single season, plus two less organized, nomadic entities: the Liosalfar (light elves) and the dokkalfar (dark elves), which will have some trading capacity.
The 4-in-one elvish "empire" will be in general very peaceful, and mercantile in nature, but will have very powerful allies in the form of various impressive "forest spirits" (based on plants and trees, but more various than just entlike beings) as well as guardian animals and animalmen, forest trolls, and various creatures of faerie.
Each division of the "empire" will function only during a single season, will have a seasonal theme, and I'm going to work hard to make each quite distinctive.
The other two elf entities (liosalfar and dokkalfar) will be less peaceful in general, but also less powerful overall, with fewer allies. They will show up throughout the year, however, and have more basic, less expensive goods, overall.
I'm going to try to work out a way to mod in some kind of mercenary system, into the game, so that you can hire beings from other entity civilizations to join your Fortress, and any such elf mercenaries will probably only come from the two nomadic groups, although the elf empire entity may occasionally offer some quite powerful guardian beasts for your Fortress's protection, or some very valuable pets.
The second entity I'm going to add will be a powerful group of giantish beings. These will be a most dangerous civilization of beings, one of the least moral entities that will actually be willing to trade with you. This will be an effort to transform the "giant" semi-megabeast into something more extraordinary than a "giant human", so I'm going to give them a civilization with several subgroups, high skill in bronze crafting, unique goods and materials, including metals and alloys that can't otherwise obtained, and a fully fleshed out entity that you may either trade with, or go to war against. This will be a very risky entity to attempt to cheat or steal from.
I'll add other information as I come up with it, but this should be a nice area to put ideas for critters and entities.