Omarion Nebula
The Omarion Nebula was an interstellar gas cloud located in the Gamma Quadrant, deep inside Dominion space.

Thousands of years ago, the Changelings retreated to an M-class rogue planet inside the Omarion Nebula to escape persecution by solids where they became the Founders. The location of the  inside the nebula was kept secret, although the hundred Changeling infants sent by the Founders to explore the galaxy were imprinted with a strong urge to return to it. This impulse caused Odo to enter the Omarion Nebula in 2371, and make contact with the Founders. ()

Later that year, a joint Obsidian Order-Tal Shiar fleet entered the Omarion Nebula and destroyed 30% of the Founders' homeworld's crust. Their attack was in fact a Dominion trap, and the entire fleet was annihilated by the Jem'Hadar during what became known as the Battle of the Omarion Nebula. ()

In an alternate 2401, the Omarion Nebula was the site of the Dominion Alliance War between the Dominion Alliance and the Confederation of Earth. ()

External links 
 
 

cs:Mlhovina Omarion
de:Omarion-Nebel
nl:Omarionnevel
Nebulae
Dominion