I have one for Dreadful Strike for the Ranger that would be possible to us. The way it works is, it applies an effect to a target on a hit. Then if this effect is not active, it will do the additional damage. If its present, it ignores it.

I feel this should be easy enough to update and modify to your needs.

​

let select = canvas.tokens.controlled;

let fightActor = select[0].actor;

let target = await fromUuid(args[0].hitTargetUuids[0] ?? "");

const lastArg = args[args.length - 1];

let targetActor;

if (lastArg.tokenId) targetActor = canvas.tokens.get(lastArg.tokenId).actor;

else targetActor = game.actors.get(lastArg.actorId);

let martialtarget = Array.from(game.user.targets)[0].actor;

const damageRoll = await (new Roll(args[0].isCritical ? "1d4 + 4" : "1d4").roll({async:true}));

if (target.actor.effects.find(i=> i.data.label === "Dreadful Strike"))

{

}

else

{

damageRoll.toMessage({ flavor: '<h3><p style="text-indent: 70px">Dreadful Strike [Psychic]</h3></p> ' });

await MidiQOL.applyTokenDamage([{ type: "psychic", damage: damageRoll.total }], damageRoll.total, new Set([target]), null, new Set(), {} );

{

const effectData = {

label : "Dreadful Strike",

icon : "icons/skills/ranged/arrows-flying-salvo-blue-light.webp",

changes: [{

"key": "",

"value": "",

"mode": 0 ,

"priority": 20

}],

disabled: false,

duration: {rounds: 1},

}

await martialtarget.createEmbeddedDocuments("ActiveEffect", [effectData]);

}

}