Automatically restore up to 50/75/100 once your Life Total is depleted (once per escape attempt).
From Skelly; you share an Unbreakable Bond
A true and loyal friend shall always stand up for you. Even stand up to you.
To gain the benefit of the Lucky Tooth, it must be actively equipped. Changing to a different keepsake after a boss chamber will remove one charge of death-defiance (unlike the Chthonic Coin Purse which can be safely removed after a boss chamber no gold penalty).