Soldier Plenos:
Good! But don't expect this to be easy. Its spirit is so strong that it doesn't succumb to the power of the Seed. Many have promised to hunt them, but few have succeeded. Most are killed or seriously wounded in the attempt.
But you look like the type who likes a challenge, eh? I'd recommend that you go see Soldier Tenius near the center of Keucereus Alliance Base before leaving. He was injured while hunting Dius. Nobody knows more about this monster than he does.