((Once again, im neutral evil, not asshole evil. Given also with my backstory that I have morality issues where for almost every bad thing that I do, I get scolded in some nightmares, plus given the fact he's evil because of how things went down with his downward spiral to become a warlock and his quest to avenge his family, think of it as a person who was good and still holds some past of his good but the way how he went about his revenge turned him towards a path that gave him the means to do it, but it corrupted him. But he still has a sense of good, but the fact he stopped caring and people who cared about him all died, he's lost all interest in doing the right thing. Yes, he's a hitman for the shadow thieves, but if he didn't agree to aid them in slaying other thief groups, he would be chaotic neutral or chaotic good, as he doesn't respect the law but he kills bad people. Think Jacket in Hotline Miami and how he's a horrible person but he only (save for Biker, Ritcher, and that hobo) kills Russian mobsters.
Plus, I have no intention as a player and as a character to screw the party over. Hell, I get big plans for us that, after a discussion, will probably anger the DM but benefit us))
"His handwriting is terrible, but seeing what I see here, it will purge him from being a vampire spawn without stabbing him with a wooden stake. And hopefully, since it doesn't seem like it has been tested, it will keep him alive."
Edit:
((I should also note that in my 4e game I run, it's run similar to this one where I don't reveal character sheets AND I have two evil characters, but I have an unaligned paladin, a lawful good avenger a chaotic good sorcerer and a chaotic neutral warlock (the latter two had went to deal with RL so they aren't there right now, as I'm trying to take in waitlisters) and it still went smoothly, with Apiks actually being the evil f***er as a vampire. We still have fun and the evil guys are kept in check by doing more unaligned and backstory driven quests as well as other quests that can be done regardless of alignment. Right now, they're visiting the paladin's home and eventually attempting to end a civil war in Tarmalune where vampires are slaughtering everyone in their blood feud over succession. The evil character is involved since it's his family, and the good characters came along because it's righ and the neutral guys came because they work good together.
So when I say that there can be an evil character in a mostly good or neutral party without problems, it can quite easily. If anything, I make us a party of non Mary Sues. ))