Ilneval is the chief lieutenant of Gruumsh, and the Orcish god of combat, leadership, and strategy. Where Bahgtru is god of common warriors, Ilneval is god of the smarter leaders of the orcish race, though he still defers to Gruumsh. He desires nothing more than to take leadership of his Pantheon, however, and it said he has already deposed one or two other orcish gods in his climb to greater status. He's terrified of Bahgtru, however, and consumed with lust for Luthic.
Sources: Dragon magazine #62 - "The Gods of the Orcs", Faiths & Pantheons,
http://www.wizards.com/rpga/downloads/LG_Deities.zip, Monster Mythology, On Hallowed Ground