First Appearance: Tomb of Dracula #7 (March 1973).
Appearances: Too many others to list.
Years Active: Late 1890s to the present.
In the Marvel Universe the events of Bram Stoker's Dracula occurred. After the events of the novel, Jonathan and Mina Harker divorced, leading Mina to go to work for Campion Bond and eventually lead a team of operatives against The Doctor in Limehouse, all the while--
Well, okay, that's not quite what happened. I must be thinking of something else. Jonathan and Mina Harker married and had a son, Quincy, sometime between 1890 and 1897. Quincy was not allowed a normal life, however, for Abraham van Helsing began training Quincy in vampire lore as a child. (van Helsing knew fairly early on that Dracula did not die the true death in Dracula.) At the age of 16 Quincy replaced van Helsing as Dracula's "greatest and most implacable foe," perhaps because it was at this time that Dracula killed van Helsing and Jonathan and Mina Harker. (It's not know for sure exactly when Quincy was orphaned, but it would fit neatly as the cause of Quincy becoming Dracula's "greatest and etc etc etc.")
Across the 20th century Harker, along with a network of other vampire hunters, including Blade, Rachel van Helsing (Quincy's daughter), and Frank Drake, fought Dracula, fighting him several times and killing him (not permanently, however) at least once. Harker eventually killed himself in an attempt to permanently destroy Dracula.
Harker was confined to a wheelchair because of his crippled legs (Dracula's handiwork), but the wheelchair was filled with a large amount of anti-vampire weaponry, including poisoned wooden darts, radar, garlic-filled nets, and the like.