One of the advantages I’ve always found of tabletop RPGs as compared to console RPGs is the ability to talk to one’s enemies, whether it’s face to face, by distant proxy, even (perhaps especially) in the middle of a battle. In fact, battle banter is one of the few situations in which I will almost invariably suspend disbelief, at least as long as the dialogue is worth it, and I once found myself running a battle that I just couldn’t stand because only one of my antagonists had a functional larynx. In stories, likewise, I tend to zone out on wordless battles no matter how exciting they are, but if even one of the combatants can keep my amused, I’ll put up with a lot of unnecessary length (within reason, anyway).
So what’s it good for?
First, of course, it establishes motivation, more than evidence and conjecture can. On full-fledged villains, of course, this isn’t quite as necessary, but it helps—even when they’re lying about their own origins. But when you’re trying to set up a tragic fight between people who should be on the same side, or ones who have other reasons to want to preserve their opponents’ lives, a complete lack of dialogue and explanation can turn a tragic battle into an unholy cross of railroad and straight-out diabolus ex machina.
Speaking of motivating forces, an antagonist being willing to talk can help to ensure a desired end-of-the-conflict result, or even affect what her opponent does between battles. One of my GMs, long ago, gave me a list of tricks to make a villain who when present makes the group uneasier and when not brings them into a homicidal rage when her name is mentioned; one of the keynotes of these was speaking with a clear condescension and arrogance. On the other hand, dialogue can also help ensure that a character survives—in some cases, by establishing that they’re only the enemy through forces beyond their control or a miscommunication; in others, making them admirable or interesting enough for the primary characters to want to keep them around. Sometimes, they can do both at once, sending their audience veering from hatred to grudging admiration and back over a small number of encounters. It all boils down to figuring out which buttons to push, and trying to do that without holding conversation can be rather like trying to operate a control array with an inch of glass between you and the buttons.
It opens the plot up to conflicts beyond one on one and yours versus ours, or fists and armies. When the antagonist’s willing to talk, it might be possible to deal with individual situations through such talking. If they’re just hinting at their plans, that opens the situation up to political games and chessmastering. Bribery, bargaining, blackmail? You bet. Reverse psychology, misdirection, ego damage—all fair game. And of course, if they aren’t willing to talk, how are you ever going to set up the temporary pseudo-alliance when a (usually bigger) third party starts coming in and making a nuisance of itself?
If what you want is a recurring antagonist, talk can make it even easier, particularly if they have a way to do so over distances—any time the antagonist doesn’t fight, the antagonist doesn’t get killed. One of my favorite recurring antagonists, from a game I’m playing in, hasn’t actually fought the group at all, but it doesn’t keep her from being one of the people the first overall arc was functionally about.
So think about it: is the person you’re setting up as the arc or story antagonist willing to talk? If not, why not?