1. Cruel and Abusive: He's described as a man who physically abused his first wife and who mistreats his stepdaughter, Helen Stoner. His violence and cruelty are evident from the beginning, setting the tone for the story.
2. Manipulative and Cunning: He uses his knowledge of medicine and his position as a doctor to hide his true nature and control those around him. He is able to convince others, including the police, that he is harmless while secretly plotting against his stepdaughter.
3. Selfish and Greedy: Roylott is driven by his desire for wealth and is motivated by greed in his attempt to inherit Helen Stoner's money. His desire for financial gain overrides any sense of morality or concern for others.
4. Ruthless and Desperate: He is willing to go to extreme lengths to achieve his goals, even resorting to murder. His desperation and willingness to break the law illustrate his dangerous and volatile nature.
5. Intelligent and Resourceful: He is intelligent enough to devise a complex and effective plan for killing his stepdaughter, utilizing his knowledge of snakes and the surrounding environment to his advantage.
Overall: Dr. Grimesby Roylott is a classic villain, a fascinating and terrifying figure who embodies the dark side of humanity. He is a complex character who blends intelligence and resourcefulness with cruelty and greed, making him a truly compelling and unsettling antagonist.