This achievement will take reaching chapter 9 to become available for unlocking.
It requires two distinct components for collecting the royal arms: seven are from the story and six have requirements that need to be fulfilled.
- Path of the Fierce: Unlocks the Mace of the Fierce - Broke 50 enemies (this is when they are glowing purple and you break their attack).
- Path of the Rogue: Unlocks the Star of the Rogue - Start 30 battles with warp-strike.
- Path of the Clever: Unlocks the Bow of the Clever - Issue 50 ally commands.
- Path of the Just: Unlocks the Shield of the Just - Parry 50 times.
- Path of the Pious: Unlocks the Scepter of the Pious - 10 royal arm activations
- Path of the Tall: Unlocks the Sword of the Tall - Kill all enemies in 3 different dungeons
When you have unlocked those respected achievements and made it through chapter nine head back to the map and notice what look like tomb doors near chapters 1-5. Click on each of these to acquire one of the royal arms from above. With the last one being clicked the achievement will unlock.