So a faerie moves into an area with might:30, bringing it's aura with it (faerie aura:6), and Muspeli comes to claim the area, breaking the Jotun's chains a couple of times before the faerie leaves.
Is the faerie's might reduced by it's aura having been weakened? Are new tethers created where the aura was converted from faerie to magic? Can the faerie establish a new aura at level 6? If the aura had been completely converted would the faerie become a magical being instead?
Pretty interesting question.
I don't remember how faerie generate auras, but, if it depends on a Power, I'd say they can reset it.
This is coherent with Loki needing to be careful not to alert faerie gods.
If it doesn't come from a power, the faerie should notice the muspelly's act. There are possibilities there, one being that it would "diminish" them while creating a parallel, magical being.
It could also "create" a magical aura, while, if the faerie change roles and establish itself elsewere, it would generate a new lvl 6 faerie aura.