The Head Of The Snake is a main quest in Assassin’s Creed Mirage.
Your objective is to report to the Bureau after dealing with the four Order members.
Here’s a walkthrough and guide of The Head Of The Snake in AC Mirage.
Report to the Bureau
Go back to the Bureau in Harbiyah. The location is provided in the map.
You’ll meet Roshan there to report the progress so far.
The quest ends here. Multiple quests will be unlocked as well.