Boon of the Berserker (5e Epic Boon)
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Boon of the Berserker
You grow stronger the lower your health falls. Whenever you cumulatively lose hit points equal to one tenth of your hit point maximum, you gain a +1 bonus to your attack and damage rolls. This effect can stack whenever you lose an additional one tenth of your health. This effect lasts as long as your hit points are low enough to trigger the attack and damage bonus.