People who call for someone to come, especially in a formal or legal way.
Summoners are usually people in authority who have the power to call others to appear before them.
Examples:
The judge is one of the summoners in the court.
The summoners called the witnesses to the trial.
The summoners asked the accused to come to the court.
The summoners told the people to come to the meeting.
The summoners have the power to make people come to them.
The summoners can make anyone come to them.