Cowering Inferno requires you to light enemies on fire. You do not need to kill them with fire damage, but simply ignite them. You can do this with weapons or with skills.
- Rank 1: Ignite 25 enemies
- Rank 2: Ignite 100 enemies
- Rank 3: Ignite 400 enemies
- Rank 4: Ignite 1000 enemies
- Rank 5: Ignite 2000 enemies