Lore: They were made out of frustration by his creator and they barely gave her design before throwing them away. [Grim is genderfluid so their pronouns is they/she/he, I'll mostly use they/them because it's easier for me. You can use whichever you want though].

Grim didn't know what to do, they were frustrated at his creator, frustrated that she was abandoned, frustrated that they had no purpose. That's all they could really feel at first. Then nothing, numbness, that's what stuck with them for a long time, swapping between those two feelings.

Once they started to calm down they saw the notes that their creator had left behind: pages of concepts and ideas. It wasn't of them, but of other beings, other universes. AUs. They wanted to see these worlds, but there was the problem: how? As they spend more time in their place, they slowly figured out they could manifest things into their own magic. Portals in this case and went to one of the AUs.

Over time, they started to feel different emotions as they traveled: Happiness, Joy, Disgust, Sadness, Confusion, Fear, Love, Annoyance, but at the same time... they started seeing the people differently too. They all have a purpose, scripted maybe, but they have a purpose, created for something. Grim never had one and started to feel Envy towards them. They don't understand why they're given a reason to live but they don't have a purpose. [I ran out of ideas]

Overall Grim is pretty neutral to most people. He doesn't engage in fights much, but due to the people she's seen in the multiverse they do fight if necessary.

They've probably met outcodes like Ink but they probably don't get along well. Probably because she is confused of how he cares so much about the creators and AUs despite that his creator abandoned him.

They've also probably ran into Error or something but eh. And Stain, which depending on what Kat comes up with they either relate more to her or they feel envy. Eh, who knows maybe she gave them the travel backpack.

Oh yeah and they have different colors and shapes for different emotions which can be mismatched:

Red: Anger/aggression - [fire]

Orange: Annoyance/bored

Yellow: Happiness/joy [stars]

Green: Disgust/envious

Blue: Sadness [tears]

Purple: Confusion [question marks]

Pink: "Love" [ehhh hearts sometimes ig]

Gray: Hollow/numb

Black: Fear [exclamination points]