How do I have a weapon have two different damage types

[kyleeliason]

One of my characters has a bow that does piercing,magic damage. However I wanted to give it the attribute of changing to psychic damage instead of any other damage type if he's invisible. How do I have a weapon that can have either X type of damage or Y type of damage depending on the situation? Do I need two different weapons that he can choose from? (I don't need it automated necessarily to check if he's invisible per se, only just a way for him to choose which type of damage.) Any easy solution to this?

[Max Silver]

It seems the easiest (to me) would be to make a copy of the bow (grab the pin as DM and drag it down to copy something) then delete the "piercing, magic" and change it to "psychic, magic". I bet there will a time when attacking something that needs magic damage to be harmed, and pure psychic won't overcome the restriction. Unless you mean for the weapon to be a purely psychic construct without magical attributes. IDK, tooling with damage types can get complicated in my brain because I'm an overthinker.
To Overthink:
Monster A is IMMUNE to Piercing damage. The psychic weapon would hurt.
Monster B is RESIST -ant to nonmagical damage. The first weapon only would do full damage.
Monster C is RESIST -ant to normal damage and IMMUNE to psychic damage. The first weapon would be choice.

Personally, I'd probably just add psychic to the damage of the single bow and leave it at that. Psychic isn't an effect that comes up very often. Or better, add it as an effect.
Maybe:
IF: Invisible; DMG: psychic,ranged

[dsaraujo]

You can also use DMGTYPE

[Zacchaeus]

Either just create a separate weapon line for the psychic damage in the actions tab; or create an effect DMGYTPE: psychic in the actions tab which can be applied when needed.

[Roach]

I never used this effect so far, so I wonder: does DMGTYPE add to whatever the damage type of your next dealt damage is, or does it replace the original type?

e.g., an arrow with "1d8 piercing", effect is "DMGTYPE:acid;" is the arrow now "1d8 acid" or is it "1d8 piercing, acid"?

[Klandare]

I never used this effect so far, so I wonder: does DMGTYPE add to whatever the damage type of your next dealt damage is, or does it replace the original type?

e.g., an arrow with "1d8 piercing", effect is "DMGTYPE:acid;" is the arrow now "1d8 acid" or is it "1d8 piercing, acid"?

I have wondered the same thing as I had found in the past (long time ago so maybe been fixed) that it didn't change all of the damage to be the new type. There is a Ranger subclasses in 5E that has a power to change the damage type to all force damage and it never seemed to work properly when I used the DMGTYPE effect on him. Maybe I will go run some more tests again.

[Zacchaeus]

It adds the damage type; it doesn't replace.