Wisps

Blue, glowing balls of light. These being are totally harmless, as long as they are not provoked to an attack. Unknown by many, the Wisps are information gatherers from the dimension called "Xorinite", and trade information as well. However, should someone foolishly attack them, they will counter it with strong magic, and their teleportation ability makes it impossible to hurt them. So it is best to leave them alone to their doings.

They can only be seen in the Deep Forest or in the Spiritwood, but why is still unknown.

When encountered in Ultima IV and V, the Wisps had nothing of their later nature. They were simply hostile magical beings that were hard to defeat. This changed in Ultima VI, where the Avatar could speak to the Wisps. This was also the case in Ultima VII and the two Ultima Underworlds.

Lore
''These mysterious floating lights have been a puzzlement to many and adventurer. They seem capable of inflicting only slight physical damage, but they also seem impervious from physical harm themselves. It has been said that these strange creatures are very knowledgeable and that they come from a world other than our own.''

- from "Fellowship", Ultima VII

Notable examples

 * It is impossible to separate one Wisp from the other, since they have all a collective mind, therefore the Avatar actually spoke with the same Xorinite Wisp every time. But the biggest impact have the Wisps in Ultima VII, where they are very important to the plot, because they would tell the Avatar where to find the Time Lord, and reveal the true nature of the Guardian.