Martin tells you that he has deciphered the next part of the Mysterium Xarxes. He claims that he needs the sacred blood of one of the divines, manifest in the ancient armor of Sancre Tor in order to fulfill his mission. So he sends you to Jauffre who tells you an ancient story about the Blades and then he sends you off to Sancre Tor in western Cyrodiil.
In and around Sancre Tor are many skeletons wielding swords and axes, as well as Wraith. The Wraith will fire both Silence and Damage Attribute, and/or Damage Skill spells at you. Be cautious, particularly if you are running through the quest because the Damage spells will be most likely to drain your strength, often making you immobile. The green spells also drain attributes,and Silence you from casting Spells, but will not limit your running abilities.
When you get down to the area where the armor is kept (Across the bridge in the middle of the entry room), the player will see glowing mist. If you walk into it, you will get a journal update telling you that you must dispel the enchantment before you can reach the armor. The enchantment drains your health, but also acts as a barrier so you can't get near the armor.
To dispel the enchantment, you must find the four skeletons that are glowing blue with a misty trail. These are the Ancient Blades and will try to kill the player because the evil Underking snared the Blades in his enchantments. When you kill the first, his ghost will appear and tell you about his three accomplices that are necessary to dispelling the enchantment (Also, take a look at his items- it is possible that he will drop an Ancient Akaviri Katana which is similiar to an Akaviri Katana but slightly more powerful). Kill all four skeletons that are scattered all throughout Sancre Tor with Wraith guarding them. Once you kill the last undead Blade you need to follow him back to the main shrine. Then all four Blades will get on one knee and dispel the Underking's Enchantment. Once you get your Journal entry grab the armor of Tiber Septim. This is the same Imperial Dragon Armor Martin will be wearing when you close the Great Gate. Then leave the shrine and make your way back to Martin and the quest is finished.
The undead Blades all carry enchanted items, Rielus has the enchanted Amulet of Ansei, which has a Fortify Block enchantment, Casnar has Mishaxhi's Cleaver, an enchanted Akaviri Dai-Katana with Disintegrate Armor enchantment, Alain has Northwind, an enchanted Akaviri katana with a Frost Damage enchantment, and Valdemar has Valdemar's Shield, a shield with a useful Reflect Damage enchantment.