MechaTarrasque
Hero
Not to derail the thread, but I was thinking that it would be nice if there were fighter and rogue subclasses, like the eldritch knight and spell thief, but warlock-related instead of wizard related (maybe getting invocations instead of spells). I think that would better fit the tropes of "sucker who picks up a magic sword that is making him kill people" (more of a Glen Cook soul-sucking sword story than a Michael Morcock one) or a "thief who makes a bad deal for magic" than trying to fit those into the warlock. I also figure a fighter with some warlock toys will end up being a better straight up melee type than the bladelock will be, while still letting you get that warlock feel.