All SPELLS use the formula:
"Many spells specify that a target can make a saving throw to avoid some or all of a spell's effects. The spell specifies the ability that the target uses for the save and what happens on a success or failure.
The DC to resist one of your spells equals 8 + your spellcasting ability modifier + your proficiency bonus + any special modifiers." -Basic Rules
For me, "
your" points more to the original caster; the spell in the spell storing item belongs to the artificer more than to the current user. You might feel differently, but the RAW does not support your interpretation any better.
This does not say "not including spells cast from items". No special item rule is needed, since the rule above applies to "spells", irrespective of source.
The rule above might well apply to spells irrespective of source, what I don't agree with is who "
your" is.
Thus, my argument doesn't hinge on the point you want to make here: I might concede it without impacting my point about who "
your" refers to.
There is NO evidence to that effect. There are items an powers that have specific rules that apply to that item/power only.
I believe every or nearly every item listed in RAW uses the original caster's ability modifier and proficiency bonus, including spell storing rings. Not the holder of the item.
What you are doing is looking at specific rules for specific items, and trying to deduce a general rule that isn't printed anywhere. 5e does not work that way. Each specific rule stands alone, it is not derived from some hidden "master rule".
Recollect that my position is that there isn't any general rule provided by RAW. I don't need to defend this point. However, I am not looking at specific rules for specific items: rather all rules for all items (or at least, an overwhelming majority - all that I could find) that store charges to cast spells with.
The rule cited above does not use the word "produce" or "cast". There is no difference.
You think not, I believe so. We cannot resolve this point by debate between us. Fortunately, it is also not crucial. On my view, the intent behind "produce" is to emphasise that the artificer clearly remains the original caster.
And again, there is a general rule FOR SPELLS. It does not specify that it only applies to spells cast by a person. That is what GENERAL RULE is.
The rule that you want to claim is general and applies, refers to the original caster. It is not the rule you are looking for
