This guide will tell you where to farm for Impact Mods in Warframe.
The impact mods, full contact, pummel, crash course, and collision force can all drop as a drop reward for killing or capturing an eidolon teralyst. You can find them on the plains during nighttime.
Since you are going to farm the teralyst for the mods, once you kill the teralyst, you have to go back through the gate. And then come back to the plains, so the teralyst respawns as long as it’s nighttime.
