Envy could be interesting; the lamia loves the BBB and envies everyone who is prettier (has higher appearance score) than her. She seeks to become queen/goddess of beauty, be desirable but deny anyone to touch or defile her beauty (expect her beauty is open to abused by BBB whom she loves).<br/><br/>So she mostly seeks to kidnap/kill all beautiful women which she sees as 'competition' for her title she wants. She could be decent beauty (perhaps +6 to appearance via race + any points invested) but she could be enrage mode vs succubus.<br/><br/>So sense her sins are envy&vanity combined. She adores having beautiful pupils, servants, slaves (under charm spell or minds broken etc) but if anyone gets prettier she kills, simple as that. Also she could seek possess anything beautiful as well (object wise, example conquer most beautiful city in world as her capital).<br/><br/>Lust other hand could also work but instead beauty she is seeking pleasure at cost of everything else. You can make outsiders if you want, but I like wide amounts of diversity but as said; you have freedom design to create the three sins.<br/><br/>I just wait until you decide or get inspiration to call what your 3th sin is :). So I myself also can get design a concept. So Envy and Lust would be your list for sure?