This is the
threat metre (or meter for the americans
) that the guild uses. Its useful in parties and raids in instances.
When you turn it on, it will show the amount of threat that your char generated.
When your damage gets too high, your threat will increase a lot and the monster will aggro on you.
Therefore, try to stay under the threat of the tank.
If a party member don't have omen, the other party members also cannot see the threat this is being generated
by that particular member.
In conclusion: Get Omen
helps a lot in party/raids
Omen threat metre info and download:
http://wow.curse.com/downloads/details/9101/