Master's Libram is a Hardmodesummon weapon. It spawns one of six possible spell book minions that fly around and attack enemies by launching a corresponding spell projectile at enemies. By right-clicking, the player can alternate between the six possible spell books. Like other minions, these spell books are invincible and follow the player for an unlimited amount of time, unless the player dies, summons a replacement minion, or cancels the buff.
Its best modifier is Ruthless. The Mythical modifier provides the widest array of stat bonuses, but these primarily affect the initial summon rather than the resulting minion. Additionally, Minions cannot deal critical hits. The only significant advantage a Mythical Master's Libram has over a Ruthless one is knockback.