This guide will tell you where to farm for Fracturing Wind in Warframe.
Fracturing wind can drop from certain infested enemies, which you can find on just about any infested tileset/missions.
The specific infested enemy you will look for is regular chargers, which can spawn in just about any infested mission/dark sector. You can run whatever mission you choose; the recommended one spawns many enemies or is endless, extermination, survival, defense, etc. However, you can usually go to Tikal on earth since many charges spawn and are relatively low level.
The mod has a relatively low drop rate, so it will take you a bit of killing/farming the chargers before the mod drops for you. If you have Nekros, it is recommended to use him to get extra drops from the chargers.
