Curse of Strahd
Deadly assassins, as the name implies.
In the Campaign:
Chapter 1: Welcome to Barovia
A small group of these assassins somehow snuck aboard the Lightningrail that the party was taking to Albia and attacked them in the night. They were all killed by the party but one; he killed himself with a cyanide capsule in his tooth before he could be questioned.
Chapter 4: The Town of False Smiles
It was revealed that the assassins were under “Santiago Montoya’s” orders to attack them on the train. It was also discovered that they were not trying to kill Elizabeth, but scare her away from Albia, back to Cormyr.
This order of assassins from the Burning Lands owed “Montoya” a favor from an unknown incident that occurred decades ago. To pay this debt, they were sent to scare Elizabeth back to Cormyr, by cutting her neck lightly and intimidating her. Things didn’t go as planned.