The Ninja Hams loyally serve him and assist him with whatever he needs.
Devil-Ham doesn't seem to take his responsibility for Ham-Ham Land very seriously; he seems more concerned for his extensive seed collection. Or well, at least he did in the past. Not much is known about what he was before he became bent on the Enchanted Sunflower Seed, but it seems as if he was a prominent member of the park.
Devil-Ham is very cat-like in terms of his species, in traits both physical and behavioral. He has sharp claws, he's very reclusive, and he has a bad habit of licking his paws, which Fairy-Ham scolds him for.He is very greedy and selfish in terms of personality and is very unconcerned with other's feelings. Towards the end, however, he decides to let Hamtaro have the Enchanted Sunflower Seed and even helps Hamtaro get back home to Laura.
He has an interesting relationship with Fairy-Ham, and she can easily sway him with a bit of her yelling at him.
See also: Devil-Ham/Gallery