The charm "powers down" to it's lowest stats in any stationary area, such as a camp. This results, for me anyway, is 50 AC, 728 HP, 693 Mana, 693 End
To temporarily "power" it back up one needs to keep running fairly lengthy distances around the zone. You cannot simply run around your camp to keep it "powered" up.
So...while the charm has very atractive stats at full power....it simply doesn't last in most gameplay situations.
This is one of the quirky Charms that powers upto 125% base. The screenshot is accurate.
We (and Lucy) don't understand charm power as well as we'd like. If anyone has additional insights into how the various charm formulae and power multipliers work, please send them to eqteam@allakhazam.com.