Personal Shield

When the war against the Wraith began the Ancients developed a small portable shield to protect them on their field trips.
While it can only block out physical damage, which means you can still drown, starve or asphyxiate in rock-slides among others, it has saved many Ancient lives from surprise attacks and / or finding themselves among a horde of enemies.

It will protect you as long as you carry it on your inventory and it has energy. After it depletes there's no recharging it.