Ethan McMillan was born in 1877 alongside his twin brother Nathan to Agnes and Owen McMillan. Like his brother, from a young age he developed an obsession with a particular hobby (the act of surgery and surgical devices).
On the Halloween night, 1891, he donned a mask similar to a bug (Probably an Arachnide Pulxis) as part of his costume. The mask was seen in the floor between Ethan and Nathan before in an old photo (dated Halloween night 1887) of the twins playing, became a significant part of "Colonel" outfit.
After the events of the Halloween night, the twins and their friends were adopted by Baxter Anderson.
With the clinic founders death, it can be assumed that Ethan took control of the clinic and became the principal surgeon.
As the owner of the clinic, he started to take patients and operate them to create horrible creatures like a floating fetus, a goat abomination, a traumatized patient. Helped by Mary Williams, his assistant.
Despite the years, he still is in Forgotten Hill looking for more patients.
