The Warlock - can be person or situation.
The Baroness - always a specific person(s).
Masquerade - always a situation.
It's always best to check surrounding cards with The Warlock, as his influence is mutable. He could represent a person who creates out of pocket expenses for you, or outright steals from you - or simply something that creates delays and obstacles in your plans.
The Baroness is the one to keep an eye on. This card will always show a person (or people) acting against you, but it won't always be obvious who as they may appear to be friendly. It won't necessarily be a female either, despite the card's character.
And finally Masquerade will always relate to a situation, it might not be as serious as The Baroness, but tread carefully.
Union is a more settled and committed relationship. It doesn't have to be a marriage, it could also represent a couple who live together.