Who is Wizard Suliman from Howl's Moving Castle and what is their importance?

Wizard Suliman was the Royal Wizard to the King of Ingary. He was from Walesm and his real name is Benjamin Sullivan. Suliman attempted to defeat the Witch of the Waste by planting trees in the waste. When she got done with him, most of what was left of Suliman was cursed to roam about as a dog.