Graves is a 'Pact of the Tome' warlock.
I like the warlock, but I do find that it has been much more useful in getting information and role-playing than combat. Not that Graves can't dish out some hurt, but he's no powerhouse...I'm not sure that any of the Warlock builds are. Could also be just my build...
I've had a hard time finding the sweet spot for Graves. Trying to balance role-playing Graves properly against my experience with the game and wanting to steer the party away from disaster has been a constant battle.
I've played him much more wise than his stat would allow. He has a 7 for wisdom...but I haven't felt like I could really play him as the broken minded scion of an ancient astral demi-god. Because I have a tendency to encourage the party away from rash, or disastrous decisions, he's ended up being more of a dark and mysterious adviser to Nekodemus, which is a cool character, but you generally want your adviser to have higher than a 7 wisdom.
Bad role-playing on my part.