Coding for a bow that has a property that gives advantage on attack.

[Hanmolemon]

I have an item, the Bow of Two Arrows, which fires an illusory arrow before firing the real arrow, the effect of which is to give advantage on attacks for the first minute of combat. The monster can roll a wisdom save and if successful that monster will be immune to the effect on subsequent rounds. Im trying to figure out a way to at minimum get it to roll a saving throw for the monster on attack and if possible get it to conditionally roll at advantage on attack for the first 10 rounds if the monster has not made a save.

[estrolof]

Personally, I'd:

1. Create a Power Group on the character's Actions Tab for the weapon, called Equip: Bow of Two Arrows
2. Add a Power to that group titled Phantom Arrow
3. Add an action to that power with a CAST (for the saving throw)
4. Add an action to that same power with an EFFECT: IFT:CUSTOM(2-Arrow); GRANTADVATK; adding a duration for 1 Minute
5. Add a GM-Visible-Only effect to the owner of the bow in the CT: 2-Arrow

Before they fire the bow at the target, they perform the Cast to see if it avoids the effect. Then, if they fail, add the effect. Then shoot away.

You could PROBABLY get more complicated. You could even do WAY easy and just remember they failed...but...shrug

[Zacchaeus]

Personally, I'd:

1. Create a Power Group on the character's Actions Tab for the weapon, called Equip: Bow of Two Arrows
2. Add a Power to that group titled Phantom Arrow
3. Add an action to that power with a CAST (for the saving throw)
4. Add an action to that same power with an EFFECT: IFT:CUSTOM(2-Arrow); GRANTADVATK; adding a duration for 1 Minute
5. Add a GM-Visible-Only effect to the owner of the bow in the CT: 2-Arrow

Before they fire the bow at the target, they perform the Cast to see if it avoids the effect. Then, if they fail, add the effect. Then shoot away.

You could PROBABLY get more complicated. You could even do WAY easy and just remember they failed...but...shrug

Not sure why the 2-Arrow effect needs to be GM visible only. I'd set it up on the players action tab with targeting of Targets so that the player can apply it to the target and then the effect listed at 4 above will work.

See this series of videos on how to set up effects https://www.fantasygrounds.com/forums/showthread.php?74212-Updating-5e-effects-videos&p=654177#post654177

And also video Eight here on how to set up a power group https://www.fantasygrounds.com/forums/showthread.php?55797-How-do-I-in-Unity

[LordEntrails]

I wouldn't bother with the IFT.
Just setup an effect that expires on next roll that targets self and grants advantage. That way they click that once right before they roll the bow attack.

Or, if this is their primary weapon and they rarely use anything else, just a non-expiring GRANTADVATK and in the rare cases it does not apply they can turn it off (or toggle to skip).

[estrolof]

Was I mistaken? I was interpreting the effect from the bow as applying grant advantage to the individual hit by the bow, and not all enemies.

As for Hidden, totally unnecessary, it would just mean the Mark on self that made the effect less cutter in the PC's CT list. But, the IFT would look for the mark before applying ADV to that roll. Thus allowing the 1 click to apply at the start, and the creature can roll vs other targets and not need to worry about "do I or don't I need to disable ADVATK" - as it would detect whenever that creature attacks the archer.

Convoluted? Maybe. ;)

[Zacchaeus]

Was I mistaken? I was interpreting the effect from the bow as applying grant advantage to the individual hit by the bow, and not all enemies.

As for Hidden, totally unnecessary, it would just mean the Mark on self that made the effect less cutter in the PC's CT list. But, the IFT would look for the mark before applying ADV to that roll. Thus allowing the 1 click to apply at the start, and the creature can roll vs other targets and not need to worry about "do I or don't I need to disable ADVATK" - as it would detect whenever that creature attacks the archer.

Convoluted? Maybe. ;)
I think your interpretation is correct (that was mine too). I just didn’t see why the DM needed to add the Hidden effect when it could be easily applied by the player. I’m not with LEs solution. I think yours is more elegant.

[LordEntrails]

Doh, too tired.
Yeah, GRANTADVATK is wrong. ADVATK works just for the advantage (so does the ADV button) but would not work for the saving throw.
Do note the solution in post #2 would make the target immune to the first attack if they save. The weapon says it only gets a save after the first attack. So you would need to make the cast after the first attack.
So; apply effects to actor and target, attack, cast/make save and remove effect if needed. and repeat save every round. Too complicated for me.

[Zacchaeus]

I think only one save is needed and only if they fail do they get the disadvantage for 10 rounds.

[LordEntrails]

Emphasis mine :)

The monster can roll a wisdom save and if successful that monster will be immune to the effect on subsequent rounds

[MrDDT]

I have an item, the Bow of Two Arrows, which fires an illusory arrow before firing the real arrow, the effect of which is to give advantage on attacks for the first minute of combat. The monster can roll a wisdom save and if successful that monster will be immune to the effect on subsequent rounds. Im trying to figure out a way to at minimum get it to roll a saving throw for the monster on attack and if possible get it to conditionally roll at advantage on attack for the first 10 rounds if the monster has not made a save.

Do you use ADVANCED EFFECTS ext? The reason I ask is it has a special feature that allows you to put effects on weapons and then apply only that effect when using that weapon called ACTION ONLY.
It's very helpful in weapon base effects that you only want to trigger or detect when using that weapon.

It's free on the FORGE and it's not very intrusive as it will only be used if it you put effects on things using it. Mostly weapons is the biggest key, but if you feel frisky you can put them on NPCs/PCs/Items/Weapons, I even think other things but not fully sure.

If you do use it let me know and I can help code an effect that works pretty good.

[estrolof]

I 100% recommend that extension! It is so helpful. When combined with BCEG (if you're into extensions) it can be pretty amazing.