Fury of the Fallen

You have trained in using your knowledge in arcane and occult ways, giving you the following benefits:

• Your pool of Knowledge of a Past Life becomes twice your proficiency bonus
• Your Knowledge of a Past Life die can become larger or smaller, when you get the highest number on your die it becomes the next biggest die to a maximum of a d12 but when you get a 1 the die size decreases to the next smallest (if you land a 1 on a d4 you cannot use you Knowledge of a Past Life)
• You can expend one of your Knowledge from a Past Life die to regain 1 hit point after succeeding a death save by 15 or higher
• You are immune to being Charmed and Frightened