Using the official WotC character sheet style I made this spell sheet, especially adapted to Warlocks, because they are so different from the other casters.
It has more space than is needed for the lists of spells and invocations, but you can always draw on it. And there's an extra space in the lower right corner for whatever you want. Basically because a walorck never has enough invocations to fill that whole column
Edit: I'm terribly sorry, I uploaded this weeks ago but it didn't seem to be downloadable.... Fixing it now, with a thumbnail too
