D&D General Dealing With Monsters Nonviolently (Weaknesses, Special Bribes, etc)?

[Nefermandias]

You get what you reward. D&D gives XP for killing monsters, so players do that to gain levels. Reward your players with more XP than just killing them and you will get that. A lot will depend on you and how you play monsters. If the orcs will take prisoners and ransom them back, then your players may do the same. Maybe an adventure where the PCs assist a merchant with getting back some guards with a ransom will help cement this idea.

This is only half true. Lots of DMs now days don't even use XP and people still go for the violent solution just because fighting is fun. Besides, "grinding" for XP isn't really a thing you can reasonably do in a TTRPG.

 

[Hexmage-EN]

I decided to update the thread title to better convey my purpose for it.

The nereid from Tales From the Yawning Portal has this particular trait:

Mantle Dependent.
The nereid wears a mantle of silky cloth the color of sea foam, which holds the creature's spirit. The mantle has an AC and hit points equal to that of the nereid, but the garment can't be directly harmed while the nereid wears it. If the mantle is destroyed, the nereid becomes poisoned and dies within 1 hour. A nereid is willing to do anything in its power to recover the mantle if it is stolen, including serving the thief.

For another water creature, the water weird has this in its 5E lore:

...a water weird bound to a sacred or befouled source of water begins to take on the nature of that site, becoming neutral good or neutral evil. A water weird loses its evil alignment if its waters are cleansed with a purify food and drink spell.

I'm a fan of spells that are more situational (like purify food and drink) having special uses like this. I wish there were more examples given in the default rules.

 

[Scott Christian]

Is there any other lore about dealing with monsters nonviolently that is particularly interesting? Alternatively, what ways of avoiding combat with monsters have come up in games you've run or played in?

I have quite a few. For example, the harpy is actually a cursed person that was once a slave. They come back to wreak havoc on people because of their past. Players can try to show they mean no harm, and thus, avoid getting attacked. Of course, they do not know this and still have never figured it out.
Several other creatures are the same. The minotaur is actually lost too, and in a rage because of it; sirens are cursed mermaids, and the curse can be broken, etc.