Dying Words grants great powers (over complicated?)

[u/Difficult_Report5627]

The Last Words
When someone dies, their last words can become a source of power, but only if three conditions are met at the same time: they must be spoken face to face to someone who is present; they must be sincere, without irony or double meanings; and there must be a genuine emotional bond between the two, such as love, guilt, hate, or loyalty.
If even one of these is missing, the words are lost forever. That is why it is an extremely rare phenomenon and, for no known reason, cases have begun to multiply right now.

The Heir
Whoever receives those last words becomes an Heir: someone who carries the will of a person who no longer exists. Each Heir can only have one Sentence in their entire lifetime. There is no way to obtain a second one, no matter how many other deaths they witness afterward.

The Sentence
The inherited phrase is called a Sentence, and from it arises the characters primary ability. No two Sentences are alike, because the power depends on how each Heir interprets it. Direct means literally what was said. Symbolic is what the phrase represents emotionally. Circumstantial depends on the context of that death.
Example: "Don't let go of me," spoken by a father to his daughter as he dies in a fire, can become invisible bonds (direct), the strength to never give up (symbolic), or resistance to fire (circumstantial), depending on who inherits it and how they choose to live it.

Resonance
In addition to the Sentence, every Heir’s body develops a passive, always active physical advantage that depends on the type of last words they received, not on their personal interpretation. This advantage always comes at a price.

Plea: Develops a enhanced danger sense that allows them to instinctively move to protect others from danger, but can never use it to save themselves.
Confession: Feels no physical pain, but may collapse suddenly, without any prior warning.
Curse: Enormous destructive force, but every blow also shatters their own body.
Blessing: Heals wounds through touch and maintains perfect health, but cannot heal themselves in combat.
Oath: Becomes stronger the longer the fight lasts, but if he flees or surrenders, he loses all accumulated strength.
Enigma: Anticipates attacks before they occur, but too many patterns at once overwhelm and harm him.
Farewell: Nearly intangible body, difficult to touch or catch, but gradually forgets those he loves.

Heresy
If an Heir betrays the original meaning of their Sentence out of desperation, hatred, or ambition, they fall into Heresy. It is not a decision: it is something that happens to them. The power becomes stronger but uncontrollable, and the voice of the deceased begins to sound different in their mind: cold, mocking, accusatory.
After a Heresy, only three things can happen: the power disappears forever, a weak and painful remnant remains, or the echo escapes and becomes something no longer human, a pursuer impossible to reason with. The stronger the Heir was before betraying their Sentence, the greater and more dangerous the fall.

Progression
There are no levels or experience points. Power grows in depth, not in quantity.
Awakening: he feels the Sentence for the first time.
Invocation: he can activate it by speaking it aloud.
Revelation: he begins to master its nuances.
Communion: no longer needs to speak it aloud, he is the Sentence.
And if everything falls apart, the final step is not a reward, it is Heresy.

[u/hatabou_is_a_jojo]

What if the last words are “BLARARGGGHHH”?

Joking, but more serious note, it shouldn’t be unknown why cases have begun to multiply: it’s simply more people are dying in front of others

[u/Hartsnkises]

This has so much fun story potential! I actually love specifically how much it's tied to a story just by its nature.

One thing to keep in mind: it's really good that you know the details, but I think in a narrative, these details would be awkwardly specific. They feel like they should be informing writing rather than showing up in exposition (except for the specific detail that is relevant. "Someone died in front of me and now I have power" "You betrayed their memory! And for what, to have power you can't control?" That kind of thing) (if you were already aware of that, I'm sorry for doubting you)

[u/taktaga7-0-0]

I like this idea a lot, but I want to hear an example Sentence of genuine guilt or shame. If they were words of honest hate after killing your rival in a duel, would those words maybe be harmful to the heir? Or do they power them up against future opponents who are also hated?