THE HEROIC LEGEND OF ARSLAN: AGE OF HEROES

Betrayed from within and overwhelmed by dark sorcery, the valiant armies of Pars are overrun by the warrior-fanatics of Rucitania. Escaping the destruction of his homeland, the heroic Prince Arislan begins to assemble a group of five, extraordinary allies — a priestess, an exiled warrior, a mischievous minstrel, an insightful artist and his attendant — to aid him in his fight against the Rucitanian invaders. Together, they must build an army and defeat 300,000 trained soldiers — including the mysterious Lord Silver Mask — who has also laid claim to the throne of Pars... (Source: Anime News Network) — Description from AniList community (anilist.co).