This is precisely a portal-type nest, seemingly connected to a channel of some sub-level plane. The way this type of nest generates creatures is mostly through summoning, by means of equivalent exchange to summon creatures to serve the summoner. Brand looked at this Light Door, and expertly took out two Secondary Moon Crystals from the Dimension Hole and tossed them in. As expected, soon the Light Vortex brightened up, and then a small head peeked out from inside.
It looked like a little person three inches long, or perhaps a proportionally shrunken maiden, with long curly hair, wearing clothes as thin as cicada wings, glowing all over, without wings, yet able to lightly hover in mid-air.
She surveyed the outside from within the vortex, then suddenly flew to stand before Brand and the others, and greeted respectfully, "Hello, Lord." Her voice was thin, with a somewhat strange accent, like a foreigner articulately speaking Kruz Language.
