Kian

You've made a huge mistake. -Kian during fights where he is damaged at least three times.

Kian is the first human to protect MONSTERS in the UNDERGROUND. His soul is currently a monster soul, as a strange substance he created made his soul a monster soul, and it was the first monster soul to have a trait, the trait being ABSORPTION. Kian is also friends with GASTER, the royal scientist before Alphys