Gerson is the God of Wisdom. He's most often by the king, Asgore, given his position as his advisor.
Gerson takes the appearance of an old, elderly-looking tortoise. He also wears a Greek-styled toga with a cloth going around his waist and wrapping around his large, circular shell.
As the God of Wisdom, Gerson has shown his reliability in the wisdom he possesses. As a result, many characters ask him for advice when tasked with difficult challenges. An example of this would be when Gaster and Undyne had an argument and the former had asked him which course of action to take and which would be the wisest to take.
He's also shown to care deeply for his friends, as when he had considered the mental health of the king, Asgore, over all else. This was shown when he had left the meeting between himself and several other gods in a hurry to help console the All-father.