Tusk is a master blacksmith who dwells in the depths of Darco's Volcano where the flames burn very brightly. Even before recruiting him, he will help you out by combining old weapons and random items in order to create powerful new weapons for you.
Not much is known about Tusk's personality, other than that he is very professional and takes great pride in his work. His work is all he lives for, basically.
Tusk's allegiance will grant you two very useful benefits. First of all, he will bring his synthesizer workshop to your castle. Not only will you be able to combine weapons and random items to create a number of unique weapons for you, but you can also bring him pieces of adamantite which he can use to make extremely durable armour for you.
Secondly, Tusk is one of the stronger support characters to take along with you to battle. Every now and then, he will smite an enemy with his mighty hammer. The strength of his blow partially depends on how many times he has used his hammer to forge adamantine equipment for you.