Lingering Soul Omen, also simply called Omen (neither names are official, as the move does not have an official name), is a hidden move that was introduced in the moveset of Jin Kazama's new fighting style in Tekken 4 and reappeared in Tekken 5 and Dark Resurrection. It is a combination of two independent moves:
It was taken out in Tekken 6.
Lingering Soul Omen is based on the two of the three moves that grant Jin Ki Power. While each of the moves seperatly last 2~2½ seconds, Lingering Soul Omen last twice that (i.e. Jin is imbued with "Omen Power", officially known as "Soul Rage", for 4~5 seconds). Further more, it has the same properties as Lingering Soul during the time Jin's hands glow, and it opens the possibility of using Soul Rage moves. The concept of Lingering Soul Omen is therefore very similar to the concept of Devil Jin Possession from Tekken Tag Tournament.
Further more, like Power Stance, it repels all attacks and makes the first hit of any attack performed during the time his hands glow do guard damage.
When to use
For the most part, Lingering Soul Omen leaves the user open to attack during its animation. As with all other Ki Charge type attacks, the user will not be able to block and the opponent's attack will do more damage if it connects. More experienced players will realize that by performing Lingering Soul Omen, you will probably attempt one of its exclusive chain moves - so there may be more risk than reward.