Haley is a King Arthur prestige hero and requires 370,000 prestige to unlock.
Unit Type - Wizard: High Damage, 60% Spell Hit Rate.
Spell - Scorched Earth: Attack a row of enemies for spell damage.
Haley is a mid game spell hero with high damage and a very low spell hit rate. Haley has one of the highest Magic stat in the game, paired with his high unit count and moderate bravery/tactics stats, he's an overall good hero for mid stage.
Being a spell hero, Haley will need Enchanted Items to increase his power. However his success rate is very low and because of that it is better to skip him than to spend lot of silver and time for him.