An elicitor has the power to absorb magic from wizards within the series, though it would make sense that they could absorb the magic from the other weir as well. While they are not part of the 5 main guilds, they are at least able to spot wizards. This is described as wizards giving off a glow around them, as Seph spotted in Madison's pictures of him, and Grace warning Jason that she could still see him. With the collection of magic, elicitors, at some point, have to give off or release the magic. For Madison, she poured the magic into painting canvases to release the magic held in her. The magic then took shape as pictures from the events relating to the magic. Basically, elicitors can absorb magic and then pour it out later.
Whenever an elicitor draws in magic, they can weaken the person the magic came from. The degree of this differs and may be optional to the elicitor. This is shown when Seph's magic was absorbed, he simply felt exhausted; but when Gregory Leicester's magic was absorbed, all his spells fell apart, from the one that he threw at Madison, to his link to the other wizards. At the time, their magic may have been shorted out as well.
It seems that elicitors may have the ability to also take in magic from magical items as well. This may be limited to very powerful items, as Madison was able to absorb the magic of the stone that held a strong source of power for the guilds. However, this has been unconfirmed, as it is unsure whether it was Madison that who activated the stone, or the stone itself.
Just as wizards and enchanters appear in groups and bunches in families, elicitors also appear in groups with families, despite their rarity.
Because elicitors have to power to take the magic of a weir, they most likely also have the power to absorb the magic of a faer, though this is as of yet unproven. It is also unclear whether or not they can take the power of practitioners of The Old Religion, who may be another, older and unknown magical guild, or Anaweir given proper instruction and as stated above, the absorbing of magical items may or may not be possible.
Madison Moss (though in third book turned Dragon Heir)