Ancalagon
Dusty Dragon
oh absolutely! I wasn't recommending making a pseudo-martial characters. But there is a bit of "shadows" in the hexblade kit - the specter for example. The unearthed arcana perhaps more (I think it had the shadow of ill omen for the hexblade, and some of the invocations that didn't make it to the official version may be useful).The hexblade is awesome, but in my mind the Shadow Warlock I was thinking of emphasizes casting more than martial prowess.
Xanathar's guide has spells in it that would be good too - shadowblade, shadow of moil...