Wilhelm works for the The Brugaire Consortium, representing clients from the Near East. Trading him parts from Ultima and Omega (found in the chests that Proto-Ultima and Proto-Omega leave behind following their defeat) will cause his clients to reward you with parts of the Nashira and Homam armor sets, respectively.
Both sets of armor are Level 75. Rewards are as follows:
Wilhelm: My name is Wilhelm. I am a purchasing agent from the Brugaire Consortium. Wilhelm: I have quite a bit of respect for you adventurers. I think it is marvelous that there are people in this world who are doing their best to help others. Wilhelm: This is just a passing rumor, but I heard that several people have ventured to another world and encountered extraordinary beings...in a mysterious place, enveloped in light! Wilhelm: It is quite a far-fetched tale, if I say so myself! It would seem that such a story cannot be true and asking if you have been to such a land would be utterly ludicrous...but still, I cannot hold back my curiosity, if indeed you have seen this ethereal land. Wilhelm: By Altana! You are far more courageous than the average adventurer! Then tell me, have you seen the giant black beasts which do not seem to be living creatures, but machines with flesh and blood? Wilhelm: Truth to be told, I am currently on orders from a certain nation to seek out such a beast. Wilhelm: I am not proposing anything so preposterous as attempting to capture the creature, however. I only require a fragment from one of the beasts. If you manage to get one I would be most pleased if you brought it to me. Wilhelm: But of course, I shall not simply take without giving something in return. Wilhelm: Let this be known to no one, but we at the Brugaire Consortium recently came into the possession of extravagant armor and apparel from the Near East. Wilhelm: I may be able to make some...special arrangements... if you lend your assistance. Wilhelm: Oh illustrious adventurer, please accept my plea!