Just like Red Archer, Lancer is a very well known Servant from Fate/stay night.
This time his Master is not Kotomine Kirei, it’s Tohsaka Rin. His true name is Cu Chulainn. He is a great hero from Ireland known as the Child of Light.
He is an untamed, wild spearman who never lets up in a fight, but in his private life he is a very just, upstanding character.
Even if Lancer’s best friend were to betray him and fight for the enemy, he would laugh about how cruel fate is while engaging them in a life or death battle.
Even if he were to encounter an old enemy of his parents, as long as they are allies now, he would remain true to his oath.
Lancer is a fearsome enemy, so it’s wise not to do anything that would make him your enemy. But if he is your ally, there’s nothing left desired. He’s the hero you would most want to become your older brother (according to Moon Cell). Lancer as usual.
In Fate/stay night he developed a reputation for his “one hit kill” spear that would never seem to hit, but in EXTRA his spear is definitely lethal, and will certainly kill you if you don’t plan ahead.
The Lancer-Rin combination makes for a formidable pair that the protagonist faces off against towards the end of the tournament. …Well depending on the route it’s possible they get knocked out in the fourth round though.