Alright, so we'll start off by talking about the Sans.

This is Ren. His personality is similar to Classic's and he is also the judge of his au. Unlike Classic, Ren has a soft spot for children and though he hasn't been directly introduced to other aus, he's slightly aware of them. In his past he worked as a scientist and still occasionally practices science. He's the middle child and cares about both of his brothers deeply. (The oldest is an inserted character)
He only talks about his secrets and inner thoughts to his older brother Cambria, though he still keeps secrets from him. His brother is king of the Monsters, making Ren part of the Royal Family. He wanted to continue to wear a hood, so Cambria and him made it look more 'royal.' Occasionally Ren will put his hood up.

Ren has a strange love for pickle juice, though he doesn't like pickles. He doesn't like Frisk very much and keeps a close eye on them from the moment they enter the Monster Kingdom.

Note: The Monsters were banished from human society, but still reside on the surface in the Monster Kingdom. If a Monster wanders into human territory they will be executed and any human that helps them will also be executed. Humans, on the other hand, are allowed to enter the Monster Kingdom.

Ren's attacks are very fast paced and his attacks are more deadly than classics. His attacks are never consistent, though he has less adrenaline than Classic.