Anhora

Anhora is the Keeper of the Unicorn, who can vanish and reappear at another destination at will, as well as casting spells such as ensnaring Merlin in a vine with a word.

After Arthur kills a unicorn Anhora appears to him and Merlin, telling them that although he had not the power to lift the curse he could put Arthur through tests in order to assert whether he is worthy. Although Arthur passes the first test, proving he is understanding and generous by allowing a man to take a bag of grain to feed his family despite the fact Uther declared all looters would be executed, he fails the second when he shows he is willing to kill a man to defend his pride.

Uther decides to cut the grain supply to the people in order to feed the armies and Arthur begins to realise that because of him the people will starve.

Merlin goes into the forest to beg Anhora for one more test to prove stating he would "trust Arthur with [his] life". Anhora then captures Merlin when he follows Arthur to the Labyrinth of Gedref. He tells Arthur that there are two cups, one has water in it and the other a fatal poison, and that each of them can only drink from one cup.

Arthur purposely drinks the poison and apparently dies. However Anhora reveals that this proves Arthur to be pure of heart as he was willing to give his life to save Merlin's. As a result the curse is lifted. (The Labyrinth of Gedref)