Grundauge is probably one of the most useless, tamed beasts that Link had in his possession— or so that's what he thought when he first captured it in the deepest forest near his hometown. It was nothing unusual, just a green monster with one large eye. At that time, LInk wasn't as formidable as he is right now, and he only caught Grundauge because he was practicing his beast taming abilities.
The aforementioned tamed beast was fast, and it darted all over the place as it tried to escape Link. However, Link persevered, and the moment Grundauge let his guard down, Link used every ounce of his speed to catch up to it and made it submit to him. This was the first time Link tamed a beast without the help of his Representative, the Crimson Dagger, and it was also near this time when Link realized that he had a knack when it came to speed and agility.