Buff Interceptions

The buff system includes a powerful interception mechanism that allows buffs to modify, replace, or cancel the application of other buffs.

Interception Structure

Interceptions are defined in the interceptBuffEffects array of a buff:

interceptBuffEffects?: {
  buff: Buff;                    // The buff to intercept
  effects: BuffEffect[];         // Effects to trigger instead
  cancelApplication: boolean;    // Whether to prevent the original buff
}[]

Real Example - Profane Exchange

The best example of interception comes from the Blood school’s Profane Exchange technique:

import { Buff } from 'afnm-types';
import icon from '../assets/buffs/profane-exchange.png';

export const profaneExchangeBuff: Buff = {
  name: 'Profane Exchange',
  icon: icon,
  canStack: false,
  stats: undefined,
  tooltip:
    'You no longer gain {buff}. Instead, lose <num>3%</num> health as <name>True Damage</name> per stack you would have gained.',

  onTechniqueEffects: [],
  onRoundEffects: [],

  interceptBuffEffects: [
    {
      buff: window.modAPI.gameData.techniqueBuffs.blood.bloodCorruption, // Intercept Blood Corruption
      effects: [
        {
          kind: 'damageSelf',
          amount: {
            value: 0.03,
            stat: 'maxhp',
            upgradeKey: 'hpCost',
          },
          damageType: 'true',
        },
      ],
      cancelApplication: true, // Prevent the original buff
    },
  ],

  stacks: 1,
  priority: -1, // Execute before other buffs
};

This intercept completely transforms how Blood Corruption works:

• Normal behavior: Gain Blood Corruption stacks
• With Profane Exchange: Take 3% max HP as true damage instead
• Result: Blood techniques become high-risk, high-reward

Interception Mechanics

Priority System

Interceptions use the buff’s priority value to determine execution order:

• Lower numbers execute first
• Profane Exchange uses priority: -1 to ensure it intercepts before other effects

Multiple Interceptions

A single buff can intercept multiple different buffs:

interceptBuffEffects: [
  {
    buff: firstBuff,
    effects: [
      /* effects for first buff */
    ],
    cancelApplication: true,
  },
  {
    buff: secondBuff,
    effects: [
      /* effects for second buff */
    ],
    cancelApplication: false, // Allow original buff but add effects
  },
];

Partial Interception

When cancelApplication: false, the original buff is still applied, but additional effects trigger:

{
  buff: targetBuff,
  effects: [
    {
      kind: 'heal',
      amount: { value: 0.1, stat: 'power' }
    }
  ],
  cancelApplication: false  // Original buff applies + healing
}

Advanced Interception Patterns

Stack Conversion

Convert incoming buff stacks into different amounts:

interceptBuffEffects: [
  {
    buff: incomingBuff,
    effects: [
      {
        kind: 'buffSelf',
        buff: differentBuff,
        amount: { value: 2, stat: undefined }, // 1 incoming = 2 different
      },
    ],
    cancelApplication: true,
  },
];

Conditional Interception

Combine with effect conditions for situational interceptions:

interceptBuffEffects: [
  {
    buff: targetBuff,
    effects: [
      {
        kind: 'damage',
        amount: { value: 0.5, stat: 'power' },
        condition: {
          kind: 'hp',
          percentage: 50,
          mode: 'less',
        },
      },
    ],
    cancelApplication: true,
  },
];

Resource Redirection

Redirect resource generation to different pools:

interceptBuffEffects: [
  {
    buff: normalResource,
    effects: [
      {
        kind: 'buffSelf',
        buff: alternativeResource,
        amount: { value: 1, stat: undefined },
      },
      {
        kind: 'heal',
        amount: { value: 0.05, stat: 'maxhp' },
      },
    ],
    cancelApplication: true,
  },
];

Tooltip Integration

Interceptions do not automatically appear in tooltips, but the variables within them do. Therefore, a custom tooltip must be written to display them.

tooltip: 'You no longer gain {buff}. Instead, lose <num>3%</num> health as <name>True Damage</name> per stack you would have gained.';

The {buff} placeholder is automatically replaced with the intercepted buff’s name in the tooltip system.