Hellfire warlock is always good choice. Anyways eldrict glaive is good for reach and able bombard with AoO with large sized creature with reach weapon. But the problem is that glaive ignores completely draegloth's strenght bonus (only take it into account for attack roll but not for dmg). Hideous blow allows combined blast dmg and dmg from natural attack plus any bonuses to said natural attack (and in errata hideous blow provokes no AoO when used in melee). Of course glaive has advantage to target only touch AC while hideous blow needs hit normal AC.<br/><br/>Acolyte of Skin you cannot enter as your outsider already. But indeed there is limit for PrC's once becoming a warlock and so best is to stick being warlock or go warlock+sorcerer or wizard and enter eldrict theurge PrC. Or take cleric levels and enter warlock+cleric hybrid PrC.