One's name was his rank; he was overall leader. His communicator had the numeral 1 embossed on it, an indication of this rank. One stayed on the Ark while Two scouted Refusis II. After Two did not complete communications, One ordered a full scale landing on the planet. One planned to colonise Refusis II and destroy the Ark along with the humans.
One's plans to land on Refusis while uncertain of the conditions caused friction between the Monoids. This culminated in fighting in which most of the Monoids, including One, were killed. (TV: The Ark)