Who is Tavish from Wicked Lovely and what is their importance?

Court faery, Tavish, is an adviser to the king. He has been the Summer King's adviser since Keenan's father held the position, and he is a close friend to Keenan. Tavish and Niall are the closest thing that Keenan has to real family. Tavish often advises Keenan to be more aggressive.