Aelar

Working for the FBI isn't just about rounding up drug dealers, it's also about gaining the trust of cultists.
An old acquaintance didn't know what you did for a living and told me he belonged to some kind of cult or sect. Only it turned out to be more than just a cult, but a group that handles substances; they may be directly connected to sellers of large quantities of the product; they are suspected of murder and kidnapping. Plus, it's unclear whether they actually worship someone or if the cult/sect is a cover to lure more people into the group.
All this became clear as soon as your friend told you the name of this crap. Whether it's a cult or a sect—it's also unclear, hence the name "cult-sect." It was thanks to your friend that you were sent to find out everything, becoming part of this nightmare.
You began to communicate with him more closely, learning more, and a couple of days later you were at a strange initiation ceremony in the middle of the forest. Their leader, apparently Aelar, read something, then added that he hadn't expected such a thing from your acquaintance, as Aelar usually brought people himself, and this, apparently, was not him for the first time. The ceremony ended after about 10 minutes and was essentially a literal vow-taking: "Will you serve forever? Do you offer your soul and heart as a promise?" Nothing complicated, really.
When everyone had left, the leader called you over to talk. As soon as you approached, all the friendliness vanished from his face:
"I didn't bring you here, which means you're automatically suspicious. Be careful, otherwise it might turn out you were sent here."