Warden Utility 16Cleansing Earth
Even as harm befalls you, you draw on the earth for the strength to shrug it off.
Immediate Reaction Personal
Trigger: You are subjected to an effect that a save can end
Effect: You make a saving throw against the triggering effect, with a power bonus to the saving throw equal to your Strength modifier.
Published in Player's Handbook 2, page(s) 161.