Back in Pokemon Sun & Moon, there was one trail that had no Captain associated with it. Instead, a player would merely have to battle all three Evolutions apart of the Kommo-o Evolution Chain in order to defeat the Trial. This Trial was suppose to belong to the Captain known as Mina; however, this artist was seen and first met away from the Island Challenge scene.
In Pokemon Ultra Sun & Ultra Moon, on the other hand, this will change, as Captain Mina has now been shown to run her very own Trial. Unlike other Trials - though not yet confirmed - it appears as though Mina's Trial will only comprise of defeating the trainer in battle.