These rules were originally created by Justin Alexander. The version presented here is slightly modified from the original.
The extra effort rules represent a moment when a character digs deep and finds the inner reserves necessary to do what must be done.
The specific list of benefits that a character can gain by making an extra effort is a sampler. Players are encouraged to suggest other things that might be accomplished with extra effort. The DM’s discretion applies to any use of extra effort.
A character can choose to push the limits of their normal abilities in exchange for the character suffering some fatigue from the effort. Immediately after using extra effort, a character becomes fatigued, even if they are normally immune to fatigue. If a character uses extra effort while fatigued they become exhausted. If a character uses extra effort while exhausted they become unconscious.
A character using extra effort can gain one of the following benefits for a single round:
Activate Class Ability: Use a class ability that has a limited number of uses per day after already expending all uses of that ability for the day.
Desperate Parry: When using a combat reaction to dodge, increase the AC bonus gained by +4; or, when using a combat reaction to block, increase the damage reduction gained by 4. (Must declare before the results of the attack are revealed.)
Desperate Save: Gain a +4 bonus on a saving throw against an attack that the character is aware of. (Must declare before the results of the save are revealed.)
Desperate Speed: Move at double speed for one round or take an additional 5 foot step.
Emulate Feat: Benefit from a feat they don’t have for 1 round. The character must meet the prerequisites of the feat.
Extra Attack: When performing the full attack action, make 1 extra attack.
Focused Skill Check: Take 10 on a skill check even when they normally couldn’t.
Opportunist: Make an extra combat reaction in a round.
Prodigious Strength: Double their carrying capacity for one round or gain a +2 bonus to a single Strength check (or Strength-based skill).
Spell Boost: A caster can use extra effort to gain a +2 bonus to their effective caster level for a single spell. (Must declare before casting the spell.)
Turn the Blow: Automatically negate an opponent’s critical hit (turning it into a normal hit).
Vicious Blow: Automatically confirm a critical without making an additional attack roll. (Must be declared before checking whether the critical is confirmed.)
A character who performs an exhausting effort becomes exhausted. If a character is fatigued when performing an exhausting effort, they become unconscious. Exhausted characters cannot attempt an exhausting effort.
Intense Skill Check: The character can Take 20 on a physical skill check without expending any additional time on the check and even in circumstances where they normally couldn’t.
Recall Spell: Spellcasters who prepare their spells can use exhausting effort to recall any spell previously cast on the same day. The spell can be cast again with no effect on other prepared spells. Spontaneous spellcasters can use extra effort to cast a spell without using one of their daily spell slots.
Second Effort: The character can reroll any one die roll and use whichever result is better.