In a tense, heated, or chaotic situation, you stand as a beacon of certain leadership. Your presence is a bulwark against fear and panic. As long as a crowd has not been frightened directly by magical means, you can get a group of people to act calm and do as you ask (such as evacuating a dangerous area) in an orderly fashion without needing to roll. A supernatural situation requires a Clash of Wills. For example, if an enemy Scion of Eris sows panic into a crowd of mortals so they’ll bolt and trample each other, a roll would be made against her. If Poseidon creates a tidal wave that happens to scare people because natural disasters are terrifying, a roll would not be made against him.