3rd age mage armour is a rare set of magic armour made of the 3rd age mage hat, 3rd age robe top, 3rd age robe and 3rd age amulet. Every piece needs level 65 Magic and 30 Defence. Its value comes from its rarity: every piece is worth hundreds of thousands of PK points. In the ::bis interface the amulet has the highest magic attack of any neck item (+15, against +12 for the Occult necklace), although it has no magic damage bonus. The hat's +8 magic attack is tied with the Ancestral hat and the Virtus mask, and it is the only hat with that much magic attack that needs just 30 Defence. The hat, robe top and robe each add +1% magic damage.
To fight the Mimic you need a Mimic casket, which you can find when you finish an elite or master clue scroll. If a Mimic scroll is in your inventory when you finish an elite or master clue, you get a Mimic casket and the scroll is used up; the scroll costs 300 Slayer points in the Slayer shop. Take the casket to the Strange Casket at ::clues to start the fight.
An elite clue scroll step asks you to wear the 3rd age amulet.
Variants
In Last Man Standing games played with the Zerker build, the defensive loot can include the minigame's own copies of the mage hat, robe top and robe. They have the same stats and requirements, and they only exist inside the minigame.