The lost scion of Atlantis an ancient underwater kingdom, who you meet... halfway around the world, as an amnesiac. Seems kind of harmless at first but then she summons a pelagic behemoth in battle and the enemy drops their weapons and runs away screaming.

The bird trainer that gives you the ability and items you need to capture and tame every bird you can encounter yourself, in exchange for a bird/hunting related side quest of course.

you are the death fish monster. you try to kill the party just before the save point. lol

The NPC that once appeared for what was supposedly a one-time event, until the dev team caved in to the requests of the player base and made it an annual thing. They hang around the event area, trading kill tokens for really weird shit.

AN NPC THAT SELLS MOUNTS. THEY'RE A BRILLIANT BEASTMASTER, TOO.

havent played but
 

the protagonist from Don't Starve

end of stage villain ready to wreck of your shit unless you come to play overpowered

An easter egg character who's generally an NPC merchant and sells you weird shit like really niche potions. You can recruit them into your party via cheat codes, but they'll jokingly scold you for using cheat codes.

your own character but only if you pay for the DLC wardrobe expansion that's like, 80 dollars
one hit kills only

The fanatical wizard of rainbow unicorns you meet in order to obtain their special gem or key or piece of an amulet. :]

I would pay $80 for a DLC wardrobe expansion. Maybe.

A shopkeep who peddles arcane and supernatural wares. She lives in a seaside cavern and sends you messages with special offers via seagull.

>:D I'd LOVE to have Seagull mail! xD

That one boss that you JUST! CAN'T! BEAT! Because he's so tricky and has that one attack that does MASSIVE damage if you don't avoid it in time! x'D

Honestly... I am reminded of Raleigh from Sly Cooper lol.
So... The first "boss" of the game.

<x} I had to look him up bc I haven't played Sly Cooper since I was 6 or 7. (I can see the color scheme matches up almost perfectly! o_o;)

One of the many elegant, elemental, wise characters you meet and they give you a new power of some sort, or a treasure to unite together with the other elemental beings. :] This one being like, a beautiful leafy earth sage that lives in the forest with wooden horns.

A companion in a cyberpunk game that you first assume to be an inconsequential NPC, until they later appear in avatar form while you're trapped in cyberspace, and help you remember who you are.

During their companion quest, you slowly uncover their secret persona as one of the elite deckers/hackers who undermine government efforts to eliminate "undesirables" from inner city slums, and help them out of a bind when soured past relations catch up with them.

The first of the final bosses on a perilous climb up a mountain in a horror/fantasy rpg. An angered soul of a lost city, and keeper of the graves of the machines that used to rule the mountain mines, that stands in the way of the hero!
o.o