Yes you can mix them though I'm not as versed with Helluva.

Name: Madison Rose
Nicknames: Maddy, Mad
Age: 23 at time of death
Gender: Female
Species: Elk
Pronouns: She/her
Date of birth: 04/08/1904
Date of death: 12/18/1937
Sins: Murder and drug abuse
Sexuality: Bisexual
Personality: Mildly insane, shy when you first meet her but the more she gets to know you, the more she hangs out and opens up to you. She gets scared easily. She's normally protective of people she cares about, and she sometimes goes too deep into thought or detail about something.
Looks: She's 5 foot tall, has legs, ears, and tail similar to an elk, fur on her upper arms, brown eyes, pale skin, and an almost fragile looking upper half of her body.
Family: None
Friends: Nifty, Husker, Angel Dust, Cherry Bomb, Alastor, and Charlie.
Rivals: She doesn't really have any as of now.
Love interest: Alastor(Basic I know)
How they died: Murdered in a police stand off after snapping and starting a murder spree.
Likes: Performing in bars, reading, causing people to fear her despite her appearance.
Dislikes: People calling her shorty, feeling powerless, and coffee.
Powers: Able to summon blades like swords, knives, and even an axe. She can also teleport a short distance.
Other: Most of her time is spent performing in bars.