Determination

You've grown to recognize your limits and push yourself far beyond them in moments of dire need.

As a reaction to an effect that would reduce your HP to 0, or as a bonus action on your turn, you may enter a determined state for 1 minute.  While in this state:

• You cannot be killed as a result of taking damage, nor can you fall unconscious.
• You are not affected by any levels of exhaustion you have.
• You are immune to the Charmed and Frightened conditions.
• Any ability granted by your class, subclass, race, or feat(s) that have limited uses are now unlimited (excluding this feat).  For any ability that relies on a pool of resources, such as a Monk's Ki Feature or a Sorcerer's Sorcery Points, the pool is unlimited.  Any spells you know below 5th level or lower no longer require spell slots to cast at their intended level.

When you exit this state, you gain three levels of exhaustion, as well as regain the effects of any levels of exhaustion you previously had.  Any damage you sustained that would cause you to fall unconscious or die while in your determined state now causes those consequences.  Once you have exited this state, you cannot enter it again until you have finished a long rest.