When Mariah Crawford's colleague, Dr. James Reeves went missing in the jungles of Africa, Mariah went there to find him and hired Sergei Kravinoff to be her guide. After several months of searching Mariah found him. However, Mariah discovered that Reeves had become feral due to exposing himself to a wonder drug he created that could heal almost any wound. Reeves then gave Mariah a vile of the drug and walked back into the jungle. As Mariah followed him to try and convince him to come back to New York City she was attacked by a pack of hyenas. Kravinoff came to her rescue but was badly injured during the fight. Against Reeves warnings Mariah gave Kravinoff the serum and his wounds healed at an accelerated rate. Kravinoff's recovery was nearly instantaneous. However, Kraven became more feral just as Dr. Reeves had and started to hunt like a wild animal. Sergei Kravinoff changed so much that he even took the name Kraven the Hunter. Mariah later returned to New York City and was employed at the Hardy Foundation where she used their lab.
Several months later Kraven was able to track down Mariah. Kraven then started to wreck Mariah's lab and told her that he wanted her to go back to Africa with him. At that moment Peter Parker arrived and changed into his Spider-Man costume and confronted Kraven. Spider-Man was then able to defeat Kraven. However, Kraven vanished before he could be captured. Mariah then explained to Spider-Man who Kraven is and Spider-Man then took Mariah to Joseph Robertson's apartment because Robbie was out of town. A short while later Robbie returned home and Mariah went out of the apartment through the fire escape believing that Robbie was Kraven. Mariah eventually found an antidote for the serum and went to the Central Park Zoo which was where Kraven took Robbie and lured Spider-Man into a trap. As Mariah entered the zoo she accidentally set off one of Kraven's booby traps and was knocked into the lion's cage. Kraven then jumped into the cage and was able to fight off the lions and save Mariah. However, during the fight with the lions Kraven was badly injured. Mariah then rushed over to Kraven and gave him the antidote which returned him to normal and was also able to heal his wounds. Reunited with her love Mariah returned with him to Africa.
Mariah eventually learned that Spider-Man was mutating even furthur into some kind of inhuman creature and began to search for a cure for him. Mariah discovered a cure and when Spider-Man came to see her about a pain in his side she told him about the possible cure. However, Mariah refused to give it to Spider-Man because she did not know if there would be any side effects. Spider-Man then lost control of his anger and started to tear up her lab. To make him stop Mariah gave Spider-Man the serum but warned him against using it. Spider-Man then left the Hardy Foundation and took a vile of the cure with him. Some time later Mariah studied the effects of the serum on Spider-Man's DNA and discovered that the serum accelerated the mutation instead of reversing it. However, Dr. Crawford was unable to warn Spider-Man. Spider-Man later took the serum and grew four extra arms.
Shortly after his mutation Spider-Man returned to Mariah Crawford. As Spider-Man entered her lab she was shocked to see what the serum had done to him. Mariah then took a sample of Spider-Man's blood to hopfully find a cure for him. Dr. Crawford then revealed that Michael Morbius was missing from the hospital and that she thought he had already fully mutated and abducted him. Mariah then turns on a news report about Morbius' abduction and Spider-Man sees Morbius on the ledge of a building and goes to save him. As Spider-Man went to save Morbius, Mariah warned him that he can't because because he is ill. However, Spider-Man ignored her warnings and went anyways.
Spider-Man later fully mutated into a spider monster and began to terrorize the city. Mariah was able to synthesize a cure and then she called Kraven and told him to come to New York so that he could capture Spider-Man so that she could administer the cure to him. As Kraven arrived in New York he was able to crack Man-Spider to the parking garage of the Worl Trade Center. Kraven and Punisher worked together to subdue Man-Spider. Punisher thratened to kill Man-Spider. However, Mariah arrived and told Punisher that Spider-Man was the victim of a disease and that she could help him. At first Punisher was ready to kill Man-Spider. However, Mariah told Punisher that she knew he hunted criminals to avenge the death of his family and that Spider-Man was a victim just like his family were victims. After hearing what Dr. Crawford had to say he realized that he was wrong to try and kill Spider-Man. Mariah then ordered Kraven and Punisher to hold Man-Spider down. As they did as they were ordered Mariah injected Spider-Man with the cure which transformed back into a human.
In the comics
In the comics her name was Calypso Ezili. Her real name being Mariah Crawford was original to Spider-Man: The Animated Series. In the comics she was also a Voodoo priestess instead of a scientist.
Born and raised in Haiti, Calypso was initiated into the arts of Voodoo. Meeting Kraven the Hunter shortly after his first defeat by Spider-Man, Calypso formed a love-hate attachment to him. She enjoyed seeing Kraven enraged and tricked him into attacking the wall crawler again. After Kraven's death, Calypso became unhinged, killing her sister to obtain her supernatural powers. Although killed by the Lizard, Calypso resurrected herself and clashed with Daredevil, before dying once more at the hands of Alyosha Kravinoff who is the illegitimate son of Sergei Kravinoff.
Mariah Crawford's primal cat appearance in The Return of Kraven resembles how she appeared in the comics.