Chrom is one of the main protagonists of Fire Emblem: Awakening. The prince and later the Exalt (ruler) of Ylisse. He is a descendant of Marth, the father of Lucina, and the potential husband or in-law of Robin.
Chrom assists Robin during the latter's Final Smash. When Robin activates his Final Smash, Chrom will warp onto the stage via warp staff and rush toward the opponent, and he and Robin will barrage them with attacks. Chrom will use his Falchion to attack.
Prince of the Halidom of Ylisse and descendant of the Hero-King Marth. He leads a militia force called the Shepherds that protects Ylisse. Though he can get reckless when training-things end up broken-he can be counted on in the head of battle. He and Robin combine their skills in Robin's Final Smash.
Chrom was considered as a playable character, but another "blue-haired swordfighter" from the Fire Emblem series was seen as repetitive and he was ultimately dropped in favor of Robin's magic-oriented moveset. This is mentioned by Viridi during Palutena's Guidance while talking about Robin.