Armsmaster is an innocent that appears in Disgaea: Hour of Darkness , Disgaea 2: Cursed Memories, and in Disgaea D2: A Brighter Darkness as the Sparring Partner. It increases the rate of Weapon Mastery by 1% per 1 Armsmaster. The effective cap on an Armsmaster is 1900. They are invaluable for Weapon Mastery, as the highest Weapon Mastery level is 255, which would take a very long time to attain without Armsmasters. When a character equips a (non-monster) weapon, that character receives a bonus to the weapon's stats equal to the character's Weapon Mastery for that weapon type times 5%. A character with Swords at 5 equipping a Sword will receive a 25% bonus from that Sword's stats. The Weapon Mastery cap of 255 means a bonus of 1275%. Thus, Armsmasters will help the player amass high stats through rapid Weapon Mastery gain.
For optimal Weapon Mastery, obtain a 1900 Armsmaster via Innocent subduing and combining. Find a map or Item World stage that has Attacks+1 and Invincible/Reverse Damage. Have the character with the Armsmaster continuously attack a character on the Invincible/Reverse Damage panel. The attacking character would receive 20 times the Weapon EXP per attack, greatly reducing the time to level Weapon Mastery to Level 255. It also works for spells with the Mentor Innocent. In Disgaea D2, the Sparring Partner's effect can be combined with the Cheat Shop, as the player can modify Weapon EXP up to 1000% which can be multiplied with a 1900 Armsmaster, allowing 200 times the Weapon EXP. The Armsmaster does not appear in Disgaea 3: Absence of Justice or Disgaea 4: A Promise Unforgotten, as the Weapon Mastery system is replaced with the Weapon Forte system, wherein skills are bought with Mana instead of leveling up Weapon Mastery.