Necromancer's coven

Magic, that may have been missed due to arctic zones and ice spells. My process requires elemental motes, and that creates an elemental wall.
In most examples, that is not enough for a proof of magic, it can only form an elemental barrier. For our consideration Fairy fire is a more accurate proof. A wall can not be cast surrounding anything completely. I think you can consider an elemental wall of ice, as easy as fire.
Other elements and chaos spell, I was considering. Wall of Bones, as a spell.was possible. Cast in an elemental plane, it is still a wall. A regenerating wall, is energy from an elemental plane.
Normally used to construct summoning circles, like those that appear in the highlands. They must be disrupted. The summoning circle can not be easily escaped from the inside, limited wish or wish. A wall can not normally be cast in a full circle like a constructed summoning circle.
Sorcery differing from Necromancy, in the supreme control over the environment. That can be accomplished a few ways, or alchemy was used to boost spells with an electrical induction. That is out of the blue, for this area. The use of earth shamanism, is used to earth shock, or deal with shape shifters, not recharge a installed radio.
A shape shifter of the swamp would copy the image of a cast spell, to identify the source of the spell that was cast. Then I would determine who had cast the spell in the first place.