Mutant

The Mutant is a NPC who can spawn in your house when you slay a boss or kill a eater of souls or chimeras and colect 10 ebonwood or Whatever that crimson one was called. Unlike any other NPC, no evil biome enemy will attack them nor will he leave if you have a evil biome nearby. They appears to be a mutated person with a green robe. It also fights with you and always respawns.

Quotes

 * "Jhhyyuh (Teach me your language)"
 * "Me needed some"
 * "Im always on sale- I MEAN- Sguhshi"
 * "Why do I pretend to speak gibberis- I- Forget it..."
 * "*muttering*
 * "HAH I JUST FOUND SOMETHING (When has new item)"
 * "*muttering*
 * "HAH I JUST FOUND SOMETHING (When has new item)"

Blood Moon

 * "Why are the girls moody..."
 * "THAT stylist girl said she will cut your head!"
 * "Jesus man, they get so mad at me..."
 * "I defeated that slime king!"

Hardmode Exclusive

 * "Souls, so strange"
 * "Greyeuh"
 * "Ow" (When damaged)
 * "JESUS, IM GOING TO THE NURSE" (when at half health or below and runs doubke average speed to the nurse before running back to where they were"
 * "Beep Boop, hey that Psy- Cyborg guy is pretty cool"

Lunar Events

 * "So, you finally made it that far."
 * "I'm proud to adventure with you"
 * "Heh, pillars"

Post Moon Lord

 * "YOU AMAZE ME"
 * "Good luck!"
 * "I love this place" (When has a good room)
 * "Will there be another wall?"
 * "Hey, I learned how to fight" (Can now fight with you in your adventures)

Wall of Steel

 * "Let's Do this."
 * "Woah!"
 * "Uh..." (When dead)

War Mode

 * "What next, Captain!"
 * "Need anything"
 * "(Random Gibberish)"

Mechanics
So the Mutant will adventure with you after you defeat moon lord, so now if you do multiplayer you have a extra team mate! It also mutates your items causing them to cause either buffs on you or debuffs on the opponent and changes it's colour. The mutation also makes it have the energy of a random potion meaning you will get a random boost from one of them