The Second Archive is a complementary storage system in which Servant, Craft Essence, Wisdom and Fou cards can be deposited. The Second Archive is subdivided into two separate archives, one dedicated to Servants, Wisdoms and Fous, and another which is exclusive to Craft Essences; both have certain limitations and properties:
- Each archive has a maximum initial storage limit of 100 slots.
- It is possible to expand each individual archive by purchasing an additional slot for 10 Mana Prisms, with a grand total of 100 additional storage slots per archive.
- The servant archive will only allow for Servant, Wisdom and Fou cards to be stored in.
- The Craft Essence archive will only allow Craft Essence cards to be stored in.
- Safe for some exceptions, all the cards can be moved freely between the normal storage and the Second Archive.
- Any cards stored into the Second Archive will be limited in the following ways:
- The cards will be unusable while inside the Second Archive.
- The cards will not appear and thus be unselectable within any menus outside of the Second Archive.
- Certain Servant and Craft Essence cards will not be eligible to be stored into the Second Archive under certain conditions:
- If the Servant has been selected for My Room.
- If the Servant or Craft Essence is within a party.
- If the Servant or Craft Essence is in a support slot.
- Mash Kyrielight cannot be stored in the Second Archive.
- On August 23, 2017 the game servers were put down for indefinite maintenance, Delight Works acknowledged that server data was randomly failing and erasing cards from the Second Archive of several players although said card disappearances had already been reported weeks before the sudden maintenance.
- Second Archive Expansion was increased from 20 upgrades to 30 upgrades. Maximum limit increased from 200 to 250 in the 10M Downloads Campaign event.