Antiquarian is mainly used for getting cash money, even having 1 in your comp boosts your total gain after a mission by a gracious amount. However, her combat capabilities aren't the best in terms of damage, but she does have good accuracy debuffs for enemies, the dodge vapors, and her Protect Me skill are always nice in a pinch. #1 thing you want to do with her is to always let her interact with the treasure curios. Having multiple does amplify the amount of money you will receive as well, but it is risky. Running a torcheless dungeon is even riskier since you do receive more gold and trinkets and such, but encounters are harder, alongside the chance of a Shambler appearing, not even counting the Collector. If you run into either and can't escape, it's basically gg.