Genshin Impact : Agent’s Sacrificial Knife

To obtain an Agent's Sacrificial Knife, you need to find and kill Fatui Agents over Level 40+. Upon eliminating these agents, they have a chance to drop Agent's Sacrificial Knife. Anything above Lvl 40+ also has a chance to drop Hunter's Sacrificial Knife.

To get Fatui Agents to become Lvl 40+, you need your World Level to become World Level 2 or higher. The most efficient WL to farm anything that needs Lvl 40+ is WL 4, as enemies are between Level 42 and 62. This will give you the most consistent enemy Lvl past 40+. Anything below, you will find them, but not as often.

To get to WL 4, you need to have completed the following.

• Be on World Level 3
• Be Adventure Rank 35
• Clear Ascension Quest 2

They aren't many Fatui Agents in Teyvat, so you'll have to travel a lot to get to them. The fastest way to get around is to use the Waypoints, travel around, kill everything, and move on.

The images below are where you can find Fatui Agents.