Iznu is a hero based on the regular Dune Raider Pillager, a mounted ranged attacker. He has a lot of health, fire-based attacks and skills and also has an aura effect improving nearby monsters. Being a Pillager, he also wears a Dune Raider's Pack armor. Aside from this, he's nothing special.
Aside from being quite durable, there's nothing special about Iznu. Clearing the surrounding camp area from any other Dune Raiders before engaging him makes the fight a lot easier. His attacks and skills (he occasionally casts meteors or throws a fire bomb) deal part fire damage, so having good level of Fire resistance might help.