Called Guard Source, it boosts a character's Vitality by one.
- Guard Source is a boss reward from Dark Nation for after fight with Rufus on the roof of the Shinra Headquarters.
- In Kalm in the last house in a row, there is a Guard Source upstairs in the cabinet to the left of a girl.
- In Junon the last house in the first area on the 3rd floor (next to the soldier guarding Beginner's Hall) has one.
- In Wutai's Turtle's Paradise Bar, the player can get a Guard Source as part of the reward for completing the "Turtle's Paradise Bar Flyers" subquest.
- In the City of the Ancients, there is a Guard Source in the first house the player comes across when going right from the intersection.
- Once the player has the Highwind, they can head back to Rocket Town and go to the item shop (with the old man outside) and find a Guard Source in the room behind.
- When returning to Midgar to stop the cannon, just after the fight with the Turks in the winding tunnel, the player can head down instead of up. Guard Source is found in a chest along the way.
- At Northern Cave there are three Guard Sources: the first is down the spiral path, in the second chest; at the next screen the player is given a choice of going right or left, and choosing right finds the second source; Continuing right, to an area that looks like a maze, and jumping off the ledge, and choosing right again, the player stands on the right end of the ledge, facing left to jump up -- inside the cave there is a chest that contains the last one.
- Guard Sources can be morphed for from Unknown 2, Bagnadrana, Spiral, Maximum Kimaira and Armored Golem.
DEF Boost can be bought for 500 Gil and raises Defense by 1.