ON THIS WIKI
Arc Amplification is an enchantment to Ethereal Familiar, which will double its damage for each level upgraded. In order to upgrade the Familiar with a certain level, it has to be already upgraded with the previous level of enchantment.
Thaumcraft 4 Research Notes
What does the scouter say about its power level?
"By concentrating more arcane energy into the wisp, its attack power is effectively doubled.
Consumes 0.03 Ignis Vis per attack and level."Aspect the Ethereal Essence is related to has to match the Aspect the Ethereal Familiar is related to and the 4th aspect in the recipe. In this article it is
Arc Amplification I
Arc Amplification II
Arc Amplification III