Astolfo

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.

Also, while Astolfo may be weak, their numerous Noble Phantasms received through their countless adventures are very powerful and reliable. But, it is very difficult to control Astolfo.