Shortly after the Battle of Red Rock, as King Kelvoras’ son came back to collect his body, he noticed that the Colania Dialiah was missing. Someone had taken it in the confusion of the battle. Around 100-180 years later, the half elf named Valmont wore the amulet as he seduced at least 3 married countesses and duchesses. After he was caught and hanged, one of the husbands took the amulet (not realizing that it was the artifact of a god) and put it in one of his vaults. Soon after, the man that would become the “King of Rogues“ stole it and went on to rule a large part of Korstraad during the medieval period as a crime lord. He then turned his dagger to the barbarian tribes, and was very successful in raiding them, but soon after he was eaten by a very large ourogarai (aka "dragonbear"; a "bear that could eat dire bears"), possibly Mother Bear herself. Then about 550 years later, the amulet was used in the Feywild by Rivona, the renegade whisper gnome who led the Blackwood Treants. Rivona escaped the coalition formed by signers of the Pact of Jeremiah, but was found dead a few months later without the amulet. 370 years later the Party was tasked by the Hand of Sirius to acquire it from the lake sized spirit of decay, the party finds the amulet, and battles the green goo spirit, obtaining the amulet. Morduval, a lieutenant of Swayne, implies that he may have been the one who gave the amulet to the goo, and that it had been "a successful test". Mord attacks the party to steal the amulet, but he narrowly fails and is killed in the encounter. The party then returns and gives it to the Hand of Sirius, where it remains to be studied.
Although with the effect it has on the ooze and some of the history involved with this artifact it seems that it also has a great amount of chaotic hidden potential that would either require a lot of research or is highly individualistic and different for everyone. Also to note is that everyone who used the Colana Dialiah has died at the hands of someone else, mostly gruesomely. If that is an supernatural echo how his first wielder died or if its a curse from Dialiah herself is currently not known.
The Hand of Sirius also wants to use the Colana Dialiah somehow to fight back against the Monitors, how they want to do that is really anyone's guess. (Captain America strength boosts, Iron Man suits or super-powered golems are all theories that float around about that one.)