The collective will sit within the agency and form a new "digital lab", teaming up with the existing Karmarama digital team.
Sharabi, the former head of social at Beattie McGuinness Bungay; Knight, the co-founder of de-construct; Hunt, the former head of digital at Innocent Drinks; and Bentley, the former head of technology at Endemol, all left their roles earlier this year to form the, as yet unnamed, collective.
The collective, who report to Karmarama's chief executive, Ben Bilboul, will also develop innovative digital communications and services.
Bilboul commented: "We're hugely excited to be partnering with such a fantastic team. They're the very best in the business and we're delighted they've chosen to partner with Karmarama."