The cell, Verve, will include errors and omissions (E&O) and directors and officers (D&O) coverage for captive insurance companies, risk retention groups, captive managers and various others.
Scott Simmons and Alan Lambert, who are both partners in the business, will lead the cell business.
Scott Simmons, partner at Verve, said: "Castel provides us with a comprehensive and robust infrastructure that has enabled us to bring Verve to fruition quickly, and deliver certainty to our capacity providers and wider market stakeholders."