#she's technically evil.

Undercurrent Toriel, the outsider.

Basics:

The only monster on the outside of the barrier, she's managed to get along with enough people to trade at a few ports closest to the sealed island and frequently goes back and forth to a few ports. She's capable of sailing through any type of weather by herself, which is strange, but no one really questions it.

She is kind to a fault and will offer help to anyone that she's able to, often offering free passage to the next port. No one has seemed to notice that a few have never returned.