The Hundred Changelings were a group of one hundred infant Changelings that the Founders sent out throughout the galaxy in order to gather information and explore without having to travel the stars themselves. Having implanted into them an instinctive urge to return to the Omarion Nebula in the Gamma Quadrant, the Founders did not expect any to return until the late-27th century. (DS9: "The Search, Part II", "Chimera")
Later in life, Odo recalled that when he was first discovered, "I didn't know what I was. I had no memory of where I was from. I didn't even know I had the ability to mimic other forms." When questioned by Captain Benjamin Sisko as to why the Founders would "send such helpless creatures out into space?" Odo responded that they did so "to find out if the species they encountered posed any threat. What better way to gauge another race than to see how it treats the weak and vulnerable?" (DS9: "The Begotten")
In "Olympus Descending", Laas returned two more of the Hundred to the Great Link. Odo discovered that the Hundred Changelings were actually sent in an exact pattern, in order to attract the attention of their creator, a giant Changeling. However, it was found and destroyed, presumably by an Ascendant, leading to the disbanding of the Great Link.