These devices contain a crystal which will passively siphon fel out from the air immediately around the elf; yet still allowing arcane to pass through harmlessly. They can be clipped to any piece of armor.
The badges have a gauge. Blue (empty), yellow, red, and green (full). When a badge is full, the crystal is tossed out and replaced. Typically, elves replace their badges within the yellow-to-red range of the gauge.
With Argus in the sky and Dalaran citizens suddenly becoming infected with, supposedly, a fel-induced sickness, the Highguard flew into panic. Retreating to Shal'aran, the Magitech began working on a newer, better, fel badge.
Plating mithril with lumenstone, the effects were instantaneous. With the combination of the passive fel siphon, and the natural fel-resistant metal, it drastically slowed the time the badges took to fill with fel; enabling the Highguard to continue participating in the fight against the Burning Legion without fear of corruption.
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