This guide will tell you where to farm for Malicious Raptor in Warframe.
Malicious raptors can drop from killing certain grineer enemies. Specifically, power fists can spawn in decent numbers depending on which planet/node you run the missions.
Saturn is the recommended main planet to run these missions, as it usually has a good amount of power fist spawns depending on which missions you run. It is recommended to run the sabotage exterminate or capture nodes, though you can run whatever node you choose.
The mod has a fairly low drop rate from the power fist, so it will likely take you a good amount of (kills) Runs before you get the mod.
