Anyone inveted to post new creatures and comment on those already posted, and check the numbers for accuracy.
XP 400
Tiny outsider (incorporeal, spirit)
Init +7; Senses darkvision 60 ft.; Perception +5
==DEFENSE==
AC 20, touch 10, flat-footed 12 (+7 Dex, +1 dodge, +2 size)
hp 5 (1d10)
Fort +0, Ref +9, Will +3
Defensive Abilities incorporeal; Immune critical hits,
precision damage, electricity, mind-affecting, petrification,
polymorph; Resist cold 10, fire 10; SR 12
==OFFENSE==
Speed fly 50 ft. (perfect)
Melee incorporeal touch +8 (1d3)
Space 2-1/2 ft.; Reach 0 ft.
Spell-Like Abilities (CL 1st; concentration +1)
3/day – faerie fire
==STATISTICS==
Str –, Dex 24, Con 10, Int 5, Wis 13, Cha 11
Base Atk +1, CMB +6, CMD 16
Feats Dodge, Weapon Finesse (B)
Skills Fly +23, Perception +5, Stealth +19
Languages Sylvan (does not speak)
SQ glow
==ECOLOGY==
Environment any
Organization solitairy, flock (3-6), or swarm (10-20)
Treasure none
==SPECIAL ABILITIES==
Glow (Ex) A wisp always glows as if under the effect of a light
spell. As a swift action, the wisp can reduce the glow to be as faint
as a firefly, or restore it back to its full intensity.
A wisp is a small spirit in the form of a ball of light. They can be found anywhere in the wilderness but are rarely seen during the day and come out mostly at night. The most common color of whisps is a pale white, but light icy blues, purples, or green are also not unusual.
Wisps communicate in their own simple language that consists of high ringing sounds, slight movements, and subtle shifts in brightness, but most can understand Sylvan as well.
Wisps are simple creatures and being incorporeal have no physical needs. They take all their sustenance from the energy of wild plants surrounding them, but can occasionally be seen in almost entirely barren desserts and frozen wastes, where all life is hidden from the eyes of travelers. Wisps tend to live close to powerful nature spirits like nymphs, dryads, or treants, and often serve as lookouts that serve the greater spirits as additional eyes for miles arounds.
I made wisps outsiders and used the spirit subtype I use in my campaign, but they could also easily be made into fey.