The fiend is being sought after tests showed five cats had died last week after being fed deadly anti-freeze.
In just two weeks a total of 16 poisoned cats have been put to sleep by vets with five more pets reported missing in the same neighbourhood.
Another pet is critically ill after vets diagnosed poisoning over the weekend.
All the cats live in a cul-de-sac in the May Bank area of Malvern, Worcs.
Distraught Shani Stocker, who lost two cats in just two days last week, found her family's one-year-old cat Boris lying in the garden on Monday.
She rushed Boris to the vets who diagnosed anti-freeze poisoning and he had to be put to down.
The next day Shani found her other cat Bubbles lying on the pavement suffering the effects of poisoning.
Vets diagnosed severe kidney failure brought on by anti-freeze poisoning and Bubbles was put to sleep.