- Irithyll of the Boreal Valley
- Irithyll Dungeon
- Dropped by Jailers.
- One can be found by crossing the first bridge and then exploring the floor below.
Reinforcing a Simple infused weapon will reduce the tick interval by roughly 0.217 seconds per level. At +10 reinforcement, a Simple weapon will replenish 1 FP per 2.85 seconds, or roughly 0.35 FP per second.