Hello 
A question we had with my wife regarding spells and modifiers and to which I couldn’t find a clear answer :
imagine a character with a Mark of Dreeg on an item. We then select the Scorpion constellation. Will its modifiers affect the Dregg’s infinite Gaze stats given by the component ?
Similarly, how does it work with Dregg’s evil eye (Occultist’s spell) ? Do all those spells also benefit from the various modifiers we have around our character ?
Thanks
It affects only the skills, it’s “skill modifier”, not “effect modifier” or however you want to call it. So, devotions and everything that that particular skill triggers are not affected.
Yes, the bonuses you get from the Scorpion constellation will effect Dreeg’s Infinite Gaze and Dreeg’s Evil Eye.
Does your wife have a sister?
Thank you both for your insight, but as it is, it looks like we have two contradictory answers ? 
And no, no sister, she has a brother though 
The confusion is coming from your use of the phrase “modifier”. This phrase has a very specific meaning in Grim Dawn, but you’re not using the phrase like most people do.
A skill mod is a very very specific value found on some pieces of equipment. Here is an example of a skill modifier: “40 acid damage to dreeg’s evil eye”. Maybe try rephrasing your question without using the term “modifier”, since skill modifiers don’t exist in the devotion tree, so I’m not really sure what you’re asking anyways.
as snazz said, modifier has a very specific connotation with this game, but, what I assume you mean is: “does the acid and poison damage % bonuses from scorpion affect my skills?”
the answer is yes, those stats affect ALL damage of that type, so if you see +100% damage to poison, you get 500 poison damage over 5 seconds as opposed to 250/5s.