Hey y'all

So as the title states, I've created a homebrew item for a player who is playing a fighter so, they don't have spellcasting innately within the class but because of their backstory, they've been given this homebrew item that gives them spells. I've been trying to use their CON mod as their casting modifier but for some reason, when I add the modifier for bonus spell save DC on the item, it doesn't actually work. I'm assuming it's because of the fact that they don't have spellcasting innately because I've tried it on characters that do have spellcasting and it adds the bonus but if there's a way to fix this, I would greatly appreciate the help!

Thanks!

Magic items that grant spells use a spellcaster's Spell Save DC, if the characer is a spellcaster (has a Spellcasting or Pact Magic class feature). 

If the character lacks spellcasting, the spell save, if not specified, will consider them to have a spellcasting ability of 10 (+0).

There is no way to set the DC using character stats that are not spellcasters.

You can, however set a manual save DC for the spells - which some items, like scrolls, do. It won't scale but you can always update it later if needed.

Could you explain a bit more, I've been having the same problem with a character of mine not being a spell caster recently. how can I set it. (Im slow Ik)

Quote from Tumble01 >>

Could you explain a bit more, I've been having the same problem with a character of mine not being a spell caster recently. how can I set it. (Im slow Ik)

 
When making an a magic item and adding a spell there is a box for a Spell Save DC. If you put a number that will become the Spell Save DC for the spell.

The box:

The DC showing on sheet:

-

If the item doesn't have a DC assigned and your character is not a spellcaster then the Spell Save DC is 8 + their proficiency bonus (not 10 as I put in error before).

Thanks. im now comfirmed slow.

You're not slow. This info isn't in the PHB but is in the DMG and not made very clear there, either.