You are the entire reason the protagonist is going on a quest. They will save you, even if you end up being the final boss possessed by something or possessing something. The player strives the entire game to meet you again.

You foresee the future, and the protagonists come to you for aid when they are lost.

You are the sub-villain who is completely unrelated to the villain, just wants to get to the treasure before the heroes in every dungeon. This results in a fight that can be relatively tricky, as there is always some gimmick. Each time you show up, you are more and more beat up and bloodied.

You are the mysterious entity who resurrects the player each time they die. However, as you also guard tiny floofbuns, whenever the player decides to attack one, they forfeit their right to a free resurrection and will have to go on a quest for you first before you restore them to their original form.

Veshora is the weird NPC that settles in your party's base operations as part of an appearance pack DLC. She offers witty advice and suggestions and storage space (where does everything go? No one knows...) but by far, her most important role is letting players give their party members makeovers.

he/she/it/ w/e
 

bonus after story villain or non-villain. no1 rly knows. he's mysterious as they come. a kuudere with a logical personality.
always breaking 4th walls and likes to make ppl gamble a lot judgments based on card games
fight him if u want to access a photo gallery of all the HQ pngs u collected during your game runs (and maybe sth more...like backstories, behind the scenes, 4th wall gameplay mode, etc.)

That glitch character who’s kind of an easter egg, hidden in a room only accessible via messing around with .ini files. Calls you a cheater when you try to talk to them. Model is made of bits and pieces of every boss in the game.

The one interdimensional, time travel character that ties into a future or past series, is there for lore purposes and gives the main protagonist mysterious hints and messages and maybe even a cheat code or two.

So like... M'aiq the Liar?

The shopkeeper-with-wanderlust who supplies your party during the first area of the game, and then joins your party once you move onto the next area.

You know, I've never actually played WoW, which is odd, considering I've played practically every big-name MMORPG out there.

Hrm... The once-a-year event NPC and her drider friend who hangs out in the town square for two weeks during the Halloween season; you can get event currency from most in-game activities and trade them to her for various goodies and buffs.

:D Ohhhhhh! I see it yeahh, *has played WoW* But with like, a Dragonhawk.
But also...

the one-time enemy in a RPG that turns out to just be the quest character who later is visted again and gives the player something useful in exchange for a rare item they really want a lot of. x}

A quest giving NPC who shows up in the strangest locations, with no reason given as to how she got there before the main character(s). May or may not know all sorts of random trivia about the location that incidentally is helpful for a puzzle nearby

An observer in shadows that changes peoples knowledge level about you when you are cought by their sight?

Fallen angel with ambiguous morals that leave you questioning whether they can really be trusted

A spider boss with minions that are unexpectedly evil duckies instead of spiders. x}