Part of the Cogwork Citadel's job is the measurement and calibration of the cosmos, and this piece of equipment is one that fits the theme. I had initially envisioned it to be more like a Geiger counter, but I figured, why bother with boring old rectangular shapes?
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Cogwork calibrators use arcane counters to measure and define the properties and characteristics of magic on the Material Plane. Such counters are typically attuned to certain planes as they tend to follow different rules of magic.
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Arcana Counter
Wondrous item, rare (requires attunement)
While holding this device, you can cast detect magic from it at will, which additionally manifests as a series of clicks. If you detect a spell's magic this way, you also learn the level at which it was cast.
Identify Traces. When you cast detect magic from this device, you can modify it so that it also identifies the presence of residual magic. You sense the presence of magic in a 30-foot radius centered on you as if you had continually cast detect magic in your location for the past hour, which allows you to see faint auras indicating magical creatures or objects that have been in the area. Once you use this property, you can't use it again until the next dawn.
Very Rare Variant. When you use this device's Identify Traces property, you sense the presence of magic as if you had cast detect magic within the past 8 hours instead of 1 hour.