5: Binding Vows

The Concept of a Binding Vow

A Binding Vow (Keiyaku) is a supernatural contract that allows sorcerers to amplify their power by placing conditions and restrictions on themselves. Unlike ordinary agreements, Binding Vows are not just psychological promises — they are enforced by the very laws of cursed energy and reality. If the conditions of a vow are fulfilled, the user gains a tangible benefit. If the vow is broken, reality punishes them, either by stripping them of the granted power, weakening them, or exacting a deadly consequence.

Binding Vows work because cursed energy is rooted in human emotion and conviction. A promise, especially one tied to survival or sacrifice, strengthens the connection between the sorcerer’s will and their CE. In essence, the vow acts as a catalyst: by binding themselves with rules, sorcerers refine their cursed energy into a sharper, more efficient form.

The Logic of Exchange

The underlying principle of Binding Vows is equivalent exchange — the greater the restriction, the greater the potential reward. The system rewards commitment and sacrifice. For example:

  • Limiting one’s speech (like Inumaki with Cursed Speech) amplifies the power of each spoken word.

  • Restricting the use of a technique to certain conditions makes it explosively powerful in those circumstances.

  • Imposing time limits allows sorcerers to briefly reach beyond their natural limits.

The trade-off must be meaningful. A vow like “I’ll blink before using my technique” would not empower the sorcerer because the condition carries no real sacrifice. The vow must introduce genuine risk or limitation — something the sorcerer cannot simply ignore. This ensures Binding Vows remain balanced and narratively compelling.

Types of Binding Vows

  1. Permanent Vows
    These are lifelong contracts, often formed unconsciously. Inumaki’s cursed speech is the result of a hereditary permanent vow — his bloodline gave up normal speech in exchange for power. Heavenly Restrictions (covered in Section 6) can also be seen as extreme permanent vows placed at birth.

    Permanent vows often shape a sorcerer’s entire identity. They may be physically or socially crippling, but they grant power that others cannot replicate through training.

  2. Voluntary Vows
    These are conditions sorcerers consciously impose on themselves. For instance, Nanami using his Overtime vow to increase his power after his shift ends. The vow is not tied to genetics or inevitability, but to the sorcerer’s will and commitment.

    Voluntary vows are flexible, creative, and situational. They allow sorcerers to adapt strategies mid-battle, crafting rules that give them an advantage when they need it most.

  3. Temporary Vows
    These are one-time agreements, often struck in desperate situations. The most famous example is Itadori’s contract with Sukuna: allowing Sukuna to take control for one minute in exchange for sparing Yuji’s life.

    Temporary vows often grant overwhelming short-term benefits but come at enormous risk. They are dramatic, dangerous, and narratively impactful.

Reality as the Enforcer

What makes Binding Vows terrifying is that they are not “self-policed.” They are enforced by the metaphysical laws of the Jujutsu world. When a vow is broken, the consequences are unavoidable. A sorcerer cannot simply ignore their restriction; if they do, their CE itself destabilizes, collapsing their technique or rebounding as backlash.

This also means Binding Vows are incorruptible. No outside force can tamper with them. Once made, they are absolute, creating a terrifying layer of commitment. A reckless vow could cripple a sorcerer for life. A carefully designed vow could make them unstoppable.

Strategic Use in Battle

Binding Vows thrive on creativity. Because they are self-imposed, sorcerers can tailor them to their techniques and fighting style. Some might vow to limit their attacks to once every ten seconds, increasing the impact of each blow. Others might vow to only use their ability on certain targets, enhancing precision. The options are infinite, making vows one of the most versatile tools in the system.

This is why experienced sorcerers often appear “smarter” than their raw power would suggest. Their mastery lies not just in energy output but in how they negotiate with reality, turning restrictions into strengths.

Expanded Lore and Philosophy

Philosophically, Binding Vows embody the human condition. Humans are defined by limits — mortality, weakness, vulnerability — and yet through those limits, they achieve greatness. Binding Vows externalize this truth, showing how sacrifice and restriction create strength. A vow is more than a trick; it is a declaration of identity. What a sorcerer is willing to give up reveals as much about them as what they gain.

This also explains why vows are so dangerous in your game’s lore. Some NPCs might make desperate vows, sacrificing sanity, lifespan, or humanity for power. Others might bind themselves so tightly they can no longer function outside of combat. Entire factions could form around extreme vows, seeing them as the only path to survival.

Adaptation for Your Game

Binding Vows are perfect for mechanics because they balance power with cost. Here’s how you could model them:

  • Player-Created Vows: Allow players to invent their own vows mid-combat. If the vow introduces a real limitation, reward them with increased damage, accuracy, or technique strength.

  • Scaling Risk/Reward: The harsher the vow, the greater the benefit. Example: “I won’t dodge any attacks this round” could double attack power.

  • Backlash for Breaking: If a vow is broken, impose heavy penalties — loss of CE, stunned turns, physical damage, or even permanent injuries.

  • Temporary Pacts: For high-stakes moments, players could form short-lived vows that grant overwhelming power but give control to an NPC, rival, or curse for a turn.

  • Narrative Impact: Treat vows as character development. A cowardly player might struggle to form vows, while a desperate one embraces them recklessly.

This keeps Binding Vows dynamic, dangerous, and player-driven, just like in canon.