Source: Book of Spirits p139
The spirit is able to create a fog, summon shadows or whip up a dust storm to conceal its exact location. The spirit spends a point of Essence per level of concealment (barely, partially or substantially, or fully concealed; see the World of Darkness Rulebook, p. 162) and rolls Power + Finesse. Each success extends the effect up to one yard from the spirit. The effect lasts up to a scene. Remember that the spirit suffers penalties to its ranged attacks as well while in cover.