You will need to acquire 2 parts for this key.

The first part is found in Kaesora. Down in the area by the church you will find a spawn named Xalgozian Fang (level 40). He is a twenty minute spawn with a Guardian of Xalgoz as his placeholder. After you kill him loot the Xalgozian Fang. It's no drop so you have to loot it.

The next piece is not no drop so you could possibly buy it in the bazaar. Travel to Lake of Ill Omen. In the Sarnak fortress you need to find Chancellor of Di’Zok (level 40). He's a shammy so he will have a pet his spawn timer is said to be 2 hours. He is in the back of the fortress. The Mobs in here do not see invis and there are several that walk a set path so stand around for a few minutes and whatch where the wandering mobs move so you can get the hang of when and where to fight him. Kill him and loot the Jade Chokidai Prod.

Once you have both pieces head to the Swamp of No Hope. You are looking for an NPC named Durgoz (a Froglok). You can find him near the froglok town at -250, -1800. Hand him the pieces to receive Key to Charasis.