Hi, I recently got an upgrade on my Warlock’s hexblade weapon, which upped the damage die from a d8/d10 to a d10/d12
I want to make this change by making a homebrew weapon for her, but I can’t figure out how to change the damage dice for Longsword, since I have to choose a base weapon when making a magic weapon. Help?

You can't change the base damage die. What you could do is start with a Glaive, add Ignore Weapon Property modifiers for Heavy, Reach and Two-Handed, and then add a Weapon Property modifier for Versatile.

Start with either a glaive or halberd and add the following Modifiers, then just change the name to “Longsword.”

• Modifier: Ignore Weapon Property->Subtype: Heavy
• Modifier: Ignore Weapon Property->Subtype: Reach
• Modifier: Ignore Weapon Property->Subtype: Two-Handed
• Modifier: Weapon Property->Subtype: Versatile

Like I said, just change the name, as her Pact Weapon she will be automatically proficient with it no matter what weapon you use as the base weapon.

Thanks for the help!!

Ok but what if I’m trying to make something that doesn’t have any similar base weapon? Like for an extreme example, a sword that uses a D20 for damage 

Quote from playgamesbeawsome >>

Ok but what if I’m trying to make something that doesn’t have any similar base weapon? Like for an extreme example, a sword that uses a D20 for damage 

 
That’s not currently possible. The best you can do is take a d12 weapon and add the Versatile property. That will make the weapon 1d12 (1d20).

Can you change range then. I'm making a thread weapon and I want basically a 30 ft reach slashing whip.

Quote from AwesomeSkitty123 >>

Can you change range then. I'm making a thread weapon and I want basically a 30 ft reach slashing whip.

 
Nope, not range either.

🥲

Quote from IamSposta >>

Start with either a glaive or halberd and add the following Modifiers, then just change the name to “Longsword.”

• Modifier: Ignore Weapon Property->Subtype: Heavy
• Modifier: Ignore Weapon Property->Subtype: Reach
• Modifier: Ignore Weapon Property->Subtype: Two-Handed
• Modifier: Weapon Property->Subtype: Versatile

Like I said, just change the name, as her Pact Weapon she will be automatically proficient with it no matter what weapon you use as the base weapon.

I'm trying to do this for a Ranger. I'm creating a magic shortbow that does 2d6 damage. But I can't get her to recognize it with Proficiency. Is there a way to fix that?  

Quote from AGreaterMonster >>

Quote from IamSposta >>

Start with either a glaive or halberd and add the following Modifiers, then just change the name to “Longsword.”

• Modifier: Ignore Weapon Property->Subtype: Heavy
• Modifier: Ignore Weapon Property->Subtype: Reach
• Modifier: Ignore Weapon Property->Subtype: Two-Handed
• Modifier: Weapon Property->Subtype: Versatile

Like I said, just change the name, as her Pact Weapon she will be automatically proficient with it no matter what weapon you use as the base weapon.

I'm trying to do this for a Ranger. I'm creating a magic shortbow that does 2d6 damage. But I can't get her to recognize it with Proficiency. Is there a way to fix that?  

 

Use the Pistol, Automatic. You will need to add proficiency with firearms though. You might want to give this a read through.