Age of Empires II: Definitive Edition (PC) - Achievement - Haute, Haute, brief candle!
Inspire a rebellion in the second Hautevilles mission "Roger in Sicily".
The aim of this mission is to kill the 5 emirs and princes, thus capturing their cities. A side objective begins part way through the mission explaining that you can incite a rebellion in two of the cities - Prince Ayyub Zirid (Red) and Prince Ali Zirid (Teal) by bringing a Relic to their monasteries. There are 3 relics in the mission - One just North of the Teal base, one just South of the Yellow base and a third on an island in the North. Just bring one to one of the monasteries, located outside of their respective cities and the achievement will trigger. This brings some of their units under your control, weakening their defence. The achievement triggers at 12:36 in this video. You may just need to take care with your Monk around the Red Monastery as there is an enemy tower next to it.