Intricate decorative equipment is a reward from the Castle Wars minigame. When wearing the platelegs, platebody, and shield in a game of Castle Wars, you get a 20% bonus to all damage against players, a 10% bonus to all barricades and ballista, and immunity from all catapult rock damage.
Just like all of the other types of Castle Wars armour, using just one or two pieces of the armour gives a damage bonus. The damage bonus works as follows: Any one piece gives +8% damage, two give +14%, and the set gives 20%.
This would take approximately 625 hours (~24 days) to obtain the full set, and 416.7 hours (~17 days) to obtain just the platebody, platelegs and shield, assuming you won every game.
Components and Bonuses
The armour set (shield included) have stats equal to tier 50 armour, but in all 3 combat styles. The sword is equal to a Mithril longsword.