Mrs. Kersh (protrayed by Cheryl Henson), also known as Gray Kersh was a secondary form of "It" created to scare Beverly, one of the novels protagonists into leaving Derry before he was going to kill them all if they stayed.
"Mrs. Kersh" was another "form" or something that Beverly, one of the protagonists in the story, was afraid of. Similar to the mummy, wearwolf, and lepper, Mrs Kersh was a face of sorts for It, drawing off something that Beverly was scared of; from her childhood through adult-hood, some she remembered just recently.
Assuming human form
In 1985, IT assumed the form of a seemingly kindly old woman named Mrs. Kersh. When the Losers returned to Derry, IT's hometown, to kill IT for good when IT had resurfaced, Beverly Marsh, one of the Losers, went off to revisit her old home after arrival. She had been a little disturbed over lunch as IT had put several grisly objects inside fortune cookies as a welcome-home present, but Beverly convinced herself these were hallucinations, and when she knocked on her home door, she asked for Mr. Alvin Marsh, her father, but an old woman, Mrs. Kersh appeared instead. Mrs. Kersh told her that Alvin Marsh was dead, which confused Beverly, as she was sure the name on the door said "Marsh" but she misread it as "Kersh." Or so she believed. When Mrs. Kersh invited her inside as an apology for such awful news, and offered to make tea, Beverly looked round, and saw the sink where she had heard IT and IT's victims speak to her thirty years ago. She thought the events would happen again once more but Mrs. Kersh called that tea was ready. Beverly was already beginning to have doubts and the tea Mrs. Kersh poured looked thick and muddy. But she thought; it was tea, no worry. Mrs. Kersh talked about local affairs and then slowly began to change. Her teeth became yellowed and grew into fangs. Her face also began to decay. Her hair began to retreat and her scalp showed through. Beverly, knowing that the monster wouldn't attack if it thought she hadn't recognized its demonic form, said politely that she had to leave,and suddenly realized it wasn't tea at all inside her cup, but blood from the victims of Derry, and almost fainted upon realizing she had almost drunk it, but regained enough wits to know that Mrs. Kersh was immediately attacking, however Beverly got away and saw the entire house had turned into a boarded-up abandoned house, inspired by her childhood fear of the story of Hansel and Gretel. Mrs. Kersh then adopted the voice of her father, another great fear of hers since childhood, and admitted that Beverly's father secretly wanted to rape Beverly and told her that nobody who died in Derry really died. Beverly slammed the door on Mrs. Kersh and escaped, but Pennywise was outside, laughing at her hysterically, much to Beverly's dismay. Beverly, distracted by Pennywise's evil laughter, almost got hit by a delivery truck driving toward her, but she managed to get out of the way in time, only to hear IT's evil laughter again and balloons flying around her as she looked on.
In the noval, Beverly fought him off by saying that "the grackles knew his real name" which confused Pennywise and buying her time to escape.