S-Rank Hunts are rare spawns since they require some special condition to be spawned. While you do get significantly more rewards, most players partake in these to get their achievement goals in these S-Rank Hunts. These vary drastically in task, such as running over a spawn point with a minion, popping leves in a zone and sometimes weather can play a part in their spawning. 

To Monitor S ranks and Fates utilize the below webpage to get started. This works really well on mobile phone!