A mechanic that has been pretty popular over the years has been the concept of Limit Breaks. I believe this stems originally from the Final Fantasy Series, and the Final Fantasy Wikia confirms that the term was first coined for Final Fantasy VII, but the concept originated with Final Fantasy VI as “Desperation Attacks.” From the same source:
Limit Breaks are often among the most damaging moves at a player’s disposal, typically capable of destroying enemies. Several Limit Breaks have developed into various characters’ signature moves… Limit Breaks usually rely on the damage the player takes in some way. When the player takes enough damage to fill up a power meter, or they enter critical status, they may perform their Limit Break.
The mechanic has been very successful for one of the staples of the video game RPG genre. I’m considering something similar for Lost Worlds. My first thought was to allow a character that has died one more action, a “limit break” action, that would allow them to perform a powerful attack that would help ensure a memorable death. Upon taking enough damage to die, the player could decide whether their character will go “out” to potentially recover after the fight, or to use their Limit Break.
The downside is that players would only get to access limit breaks when their characters were 100% going to die. The upside is that this helps take a little of the sting out of character death, and lets characters die as heroes rather than ignominiously in a meaningless combat. It also helps the players recover from a shift in combat where suddenly the enemies have too much firepower to overcome, leading to an eventual party wipe if the GM doesn’t have mercy in some overt way.
Marvel roleplaying introduced a mechanic whereby a player could utilize the damage they’ve taken as a bonus on a roll, called “Exploiting your Stress.” Doing so allows the character to use their pain as a weapon, but it also automatically steps up their damage to the next damage level. So, if you have 4 wounds before you are dead, and you currently have taken 2 wounds of damage, you could take a +2 bonus on your next roll, but you automatically go to 3 wounds of damage after doing so. To take advantage of this, you’d have to make wounds and your core mechanic work on the same order of magnitude (damage in HP in 3.5, for example, would be a bad choice as a to hit bonus).
I’m thinking that every class will have its own limit break damage output, and the actual instance of the limit break is narrated by the player. So, maybe the thief can automatically hit an opponent with a critical hit sneak attack, and narrate how the final blow took the hero down, but the enemy wasn’t prepared for the hero to stand back up one time and thrust their sword through its back.
The exploiting your stress mechanic seems interesting as well, and could escalate and speed up combats, giving players a way to add dramatic tension when appropriate. It has to be carefully balanced though so that it’s useful in a desperate or dramatic situation, but isn’t simply used ad nauseum.
Another way of implementing this could be a power that activates in a similar way to a power that activates based on an escalation die from 13th Age, but based on something more “real” to the game, like damage taken. For example, you might be able to use certain “Desperation Powers” when your health is below 10 hp. This would help delay some dramatic/climactic powers to the end of combats rather than always firing the cannons at the beginning, which was one of the benefits I noted in the escalation die.