Basically a version of the British comedian as a supernatural being, in his evil phase Russell was basically a stalker type obsessed with Mel and wanting her to be his. This is explained in a story which tells of how he tried to capture Nathan numerous times and attempted to corrupt him and make him just like him in a lot of ways including physically and mentally, Mel pretended to be his lover for a while to get information out of him before she revealed to him that she hated him before hulking out and going into her monster-mode (basically a Hulked Out version of herself) and destroying his dark lair, Russell turned into his demonic dog-creature form but she fought back and impaled him, making him collapse on the ground before he morphed back to his regular form. Although Russell had been killed off, due to his powers he could resurrect himself which he did. After resurrecting, he pretty much went after Nathan as well as Mel and her friends both in the waking world and in the dream-world.
Using their visions/dreams as a means to do so, he went after them and altered them into nightmares in which they had to fight him and his minions or in Nathan's case...nearly end up completely turning into him. Mel's boyfriend at the time Lithius tried to use his scientific knowledge to comprehend what was going on despite not knowing how the lore of the monster world works, but he didn't believe her...this of course was the result of Russell's powers affecting victims in the waking world, and friends of the victim who are seen in said nightmares/visions having hazy memories as a result of it, hence why Lithius himself dismissed them as 'hallucinations' - he served as her main antagonist in the 2014-2016 storylines. After being nearly hunted down, he transferred his aura and soul into the body of a female human and turned that human into him to recover energy he had lost from all those battles, he later appeared and reunited with Mel, apologizing to her and announcing that he had turned over a new leaf, now only using his more demonic/energy vampire-like powers for good instead of evil.
He is half demon and half vampire, and he has somewhat of a blood addiction, or rather it is an on and off ordeal, and since he is technically a good guy now he helps out whenever necessary and like him, only goes after those who harm his friends. He also has a specific rule about turning others, and that rule is that he can turn them but he'll only do so if they want to or if they ask nicely, he is very polite regarding this method and even if he harms someone accidentally, he will always apologize (unless of course they are his enemies). He has changed a lot since first reuniting with Mel, no longer wanting to stalk her or do evil things, but rather helping her with supernatural tasks and serving as a companion and party member when she's on her various adventures. He has various powers which he uses including shapeshifting into various 80's or 90's styled vampire forms, turning into a demonic werewolf-like creature or bat-monster that look like the ones from Bram Stoker's Dracula, dream manipulation and hypnosis, the latter he uses for various things including enticing his enemies into being under his control, and he can also transform others either into half demon-like creatures, monstrous versions of him, or various horror type creatures including Night of The Demons styled 'demons', Chuds and Deadites, he can also turn females into demoness types to be his.
And also as mentioned above, should he ever find himself in a tight situation he can't escape from, he can transfer his aura and spirit into others, possessing them and turning them into him so he can carry on without any troubles. Several aspects of him parody the overly sexual kind of monsters that either have powers relating to do with sex or have a sexual aspect to the powers, of course he doesn't do sex scenes or nude scenes, he used to be like that when he was evil but that's because he was trying to embody the 'Evil Is Sexy' trope. He truly believes that there is no reason for a monster, male or female to have intercourse with human victims, and that the seduction/flirts are the best and true ways to do it - and even then, he views that unless said monster is using the seduction element to seduce their prey before they feed on them.
His more vampiric instincts seem to show a trace of him that was left over from the times he was a villain, but he is more or less the type that wouldn't hurt, kill or maim anyone unless they have attacked Mel or any other friends of his, and he'd only bite or drain them of blood and energy for survival, because he has that Sleepwalker type aspect to him only without the incest. He is genuinely friendly, intelligent and passionate despite his history of being an antagonist.