Who is Tirian from The Last Battle and what is their importance?

Tyrian is the last King of Narnia. He is well respected, a talented swordsman, and a descendant of Prince Caspian. His best friend is a unicorn. When Tirian witnesses a fraudalent exhibition, he prays that he might be helped by the friends of Narnia. He then leads an assault against the Caloremenes at the stable.