The idea of a half-witch, half-werewolf hybrid is fascinating, especially when you start digging into folklore and modern fantasy tropes. In most mythologies, witches and werewolves operate under different rules—witches often rely on magic, while werewolves are bound by lunar cycles and physical transformation. Combining the two would create a being with unique vulnerabilities and strengths. Immortality? It’s tricky. Witches might achieve longevity through spells or pacts, but werewolves are usually mortal unless cursed in a specific way. A hybrid could theoretically inherit both traits, but I’ve yet to see a definitive source claiming they’d be immortal outright. Maybe they’d age slower or resist certain fatal wounds, but true immortality feels like a stretch unless the story explicitly bends the rules for them.
That said, I love how creative writers get with hybrids. In 'The Wolf Witch Chronicles' (a self-published series I stumbled upon), the protagonist is a witch-werewolf mix who can toggle between forms at will but still bleeds like anyone else. It’s the balance of power and limitation that makes these characters compelling. If they were straight-up immortal, a lot of tension would evaporate. So, while the concept is ripe for exploration, I’d lean toward 'no' unless the narrative deliberately grants them that perk.