The Sign, made by Merlin, is originally a Compass that would point to anyone that had magic blood. However, it wasn’t that effective in a group of people and the compass would go haywire. Merlin then brought it to the elves who weren’t extinct at the time and asked for their help. In turn, the elves brought The Sign to the sirens and captured their voices which is the sound every mage hears when The Sign is activated. This is better for group settings since only the mages ended up reacting to the noises of the sirens.  The Sign is now in the hands of the Order of Royals and there is only one of its kind. Even Oh Shun, the master item charmer isn’t able to replicate The Sign as he does not have any elven magic. It’s used only when they need to seek out mages.