Colonna is the offspring of Underfell Sans and Underfell Alphys. She is the Fell version of Calisto and only comes into contact with Underfell characters.
Colonna is a skeleton-Lizard hybrid due to being born from Fell!Sans and Fell! Alphys. She wears a dark green hoodie with a red lab coat underneath. She does have a golden tooth due to being born from Sans. She also smokes as she stood up for Alphys against Asgore, which lead to her getting the worst beating yet- Asgore not only inflicted her with extreme pain in a way that everyone would remember, but injected her with an absurdly large amount of Determination-about 500 litres of the stuff. This took weeks to extract and left her with a scar down her right eye. Due to the pain she suffered, she asked Alphys for help, and Alphys put her on crack. To this day she still gets similar treatment from Asgore -that Alphys took for years- daily.
She is a fell version of Calisto and so is just a slightly darker version-except she's almost completely different. She hates Asgore and even formed an alliance with Undyne, Papyrus and Toriel to try to take him out for good. This failed however as Asgore has beaten them all hundreds of times. She also managed to get Alphys, Mettaton and Sans in on the rebellion since they needed the help that much. Truly, though, she just wishes for inner balance.
She loves soda. Alphys doesn't get on at her for it in this AU as Alphys was there to see the insanity she had suffered, and hence believes she deserves it.
She also loves blueberries.
She has a crush on Trajan.