Figure | Fate/Grand Order | Saber/Astolfo | SEGA

Astolfo is a Former servant known as the Rider of Black from the Great Holy Grail War, or he is also known as one of the Twelve Paladins of Charlemagne in the Charlemagne legend from the Anime series Fate/Grand Order. He will leave all hard decisions as a matter for his heart to decide and will do as he pleases without regret.

Fate/grand order
A grand order to fight fate has been declared—an order to change the past and restore the future. Following the events in Fuyuki, Ritsuka Fujimaru and Mash Kyrielight must restore the Foundation of Humanity by retrieving powerful Holy Grails. The Grails, which are capable of granting any wish, are also able to sustain abnormalities called Singularities that threaten humanity's existence. (from Wikipedia)

Astolfo is a character from the legend of Charlemagne, France's most famous tale of chivalry. One of the Twelve Paladins of Charlemagne, and a prince of England. Additionally, a screwed-up Heroic Spirit who has lost all rationality. The Twelve Paladins were knights who served Charlemagne, the King of Franks. Astolfo, cousin of Roland, was one of those twelve knights. However, according to legends, Astolfo was considered one of the weakest amongst the knights.

Out of control, inexperienced, careless, etc, etc. But despite such a reputation, the Knight Astolfo overcame a number of difficult tasks. By the way, Astolfo's dressed this way to calm Roland down after being rejected. Astolfo has lost all rationality, so instead of making judgements based off of merits, Astolfo makes all choices based off "if it feels good or not." That hasn't changed since being summoned as a Servant, but since Astolfo is a good person, there isn't too much to worry about.

(from fandom Fate Grand Order wiki)