Mysterious Robe

The Mysterious Robe is a Robe found in Golden Sun: The Lost Age and Golden Sun: Dark Dawn.

Basic Description by Game
The Mysterious Robe increases the wearer's Defense by 48 points, making it the strongest Robe (although the Mythril Clothes offer a slightly higher Defense rating). Any party member wearing the Mysterious Robe also recovers 20 HP and 10 PP each turn. It can be purchased for 36500 coins, making it the most expensive item in the series (it is worth even more than the mighty Sol Blade), and can be sold for 27375 coins.

In The Lost Age, the Mysterious Robe is sold in Prox and it can be equipped to Jenna, Ivan, Sheba, and Mia. In Dark Dawn, it is sold in Champa Camp and can be equipped by Karis, Himi, Rief, and Amiti.

Analysis
In both The Lost Age and Dark Dawn, the Mysterious Robe is the only piece of equipment that automatically restores both HP and PP at the end of the wearer's turn. Additionally, it has the highest HP regeneration rate of any piece of equipment. In The Lost Age, the Mysterious Robe is third in terms of PP regeneration, behind the Iris Robe and the Psychic Circlet. In Dark Dawn, only the Iris Robe restores more PP. These two traits combine to create a piece of armor that is arguably the best item in the entire series.

In general, the Mysterious Robe is a great item to give to the main healer in each game's respective party, such as Mia in The Lost Age and Karis or Rief in Dark Dawn. This grants the healer great survivability and a nearly unlimited PP supply, allowing them to keep the rest of the party alive.

In The Lost Age, there are only four Robes that automatically restore HP (the Blessed Robe, the Oracle's Robe, the Muni Robe, and the Mysterious Robe), and only four Adepts who can wear Robes. For these Adepts, there is no other equipment that can restore HP automatically, making these four Robes very valuable items. In Dark Dawn, only three such Robes exist: The Blessed Robe, the Muni Robe, and the Mysterious Robe. In this case, the Mysterious Robe becomes even more valuable, and thus the wearer of the Mysterious Robe should be chosen carefully.

Trivia

 * The Mysterious Robe, like some other items from The Lost Age, is partially coded in the original Golden Sun game cart. In that incarnation, its only effect was to increase base Defense by 40.