Blank (Left) and Vivi (Right) runing for thier lives in the Petrified Forest.
Blank is one of the members of a group of theives called Tantalus, and the main character Zidane's best friend. After they escape Alexandria with Princess Garnet, their airship engine blows up and crashes in the Petrified Forest.
In the Evil Forest, Blank helps cure the poisoned teammates who had been injured by the sub-boss. He then shows up mid-battle to the fight against the forest's master, and then joins the team in fleeing from vines and plant spiders. Just as Zidane is about to be caught by a spider, Blank pushes his way into it's grip, allowing Zidane to escape, and ultimately petrifying the young thief, though not before he throws Zidane the map of the Mist Continent.
Zidane is distraught over his friend's sacrifice, but continues on knowing Blank would have wanted it. Later in the story, it is revealed that Marcus and Cinna are planning to find a way to cure Blank, not wanting to abandon their "bro". Marcus joins Baku in Treno, intent on getting an item called the Supersoft, which can cure any kind of petrification. They get it from Dr. Tot thanks to Garnet, and after they split ways in Alexandria, Marcus frees his comrade, and together they knock out Zorn and Thorn and free Zidane to escape to Pinnacle Rocks.
Afterwards, when the team gets control of the Blue Narciss, Blank acts as the party changer, whenever you're onboard and need a party change, you just ask him. He's there to the very end, and in the final scenes is still an acting member of Tantalus, as they perform for Alexandria a second time.