[Menteith]

Vecna-Blooded Changling Cleric with the Southern Magician feat and a domain granting access to bluff as a class skill. Dedicate yourself to an Elder Evil for the perks (lots of bonus Vile Feats). Take the Persona Immersion feat and the Willing Deformity (Bonus Vile Feat) and Deformity [Madness] (Bonus Vile Feat). Congrats, you are now immune to all Mind Affecting effects, all Divination, can supply whatever false information you want if someone attempts a 3rd level or lower Divination on you (such as Detect Evil). Do typical Clericzilla stuff and stuff which makes you look like a Paladin (buff the crap out of yourself, prepare healing spells, etc).

You'll be undetectable outside of a Metacognition capable of beating Vecna's Caster Level targeting you, and can easily pass as a LG Paladin if you prepare the right spells.