Captain Finn is a companion here to help you with Beam Dots. Once he's received enough (triangular) companion dots from you, he will supply your board with Beam Dots. Beam Dots can clear all dots in a row, a column, or both at the same time once connected to similarly-colored dots.

Fill up his meter with six companion dots, and his ability will be activated. (With a boost, his meter can be filled with only four companion dots.)