Jeff holding Jessa's hamsa necklace in "Centralia"
The hamsa is a hand-shaped amulet popular throughout the Middle East and North Africa, especially among those of the Jewish faith. The hamsa is often incorporated into jewelry, art, and wall hangings as a superstitious defense against evil.
In EverymanHYBRID the Hamsa has been seen in three places. Damsel posted a photo to her blog of small ceramic tiles that bore the symbols, with the caption "Thinking of hanging these around the place. I hope they… work?"
Jessie can be seen wearing a necklace with the symbol during A Day with Green Feathers. The EMH guys later confirmed in a Livestream that Jessie is Jewish.
Most importantly, Jeff gave Jessa a hamsa necklace during the 7/24 UStream which has become an important symbol to him during the time that she has been missing. When Jeff found the necklace during Centralia he took it as confirmation that Jessa is dead. During the first Trial of The Seven Trials Of Habit Jeff buried Jessa's hamsa "near an old viaduct where [they] went to a picnic one time."
Despite its intended use, the hamsa has shown no effectiveness against the evil the cast is fighting against.