I am in the Gauntlet of Shar. I found that I can steal Yurgir's Unberil Gem vs. fighting or helping him. He attacks but I can sneak out and avoid the fight.

If I choose this option, will this damage the game's Act 2 or 3 plot line?

Note. This idea was based on a internet suggestion so I know that others have attempted this option.

Thank You

It should not have any major impact on the choices available to you in act 3.

I have played through twice and both times I fought Yurgir so I can't say exactly what would happen if you help him or avoid him. But I do know what happens if you do fight him and it has little impact on the plot.

If in act 3 you chose to go down a certain path and resolve it in a certain way then in the pre fight banter you get a dialog option that if you pass the skill check the fight will be easier. If you avoid Yurgir you probably won't get the option to make the fight easier then again the fight may already be easier through avoiding Yurgir.

Sorry my post is so vague but I am trying to avoid any spoilers as you are only in act 2.

His whole question is basically a request for spoilers.

I don't know what happens if you take this route, but that's kinda the fun of the game. Try it, see what happens. Maybe it'll be awesome, maybe it'll suck. What I've found so far is that there are only a handful of things that are dramatically game-altering - things that cause your companions to leave, and even that can be remedied with mercenaries, you just don't get to hear their stories.

The cool thing is that you can run through the game multiple times and try different things each playthrough.

if you don't want to take that time, just make a save before you do something you think is dramatic, and only replay from that point.

it makes zero difference to the plot

do miss out on a small amount of exp and loot of course but Larian didn't allow for that outcome beyond letting you try it

If you help Yugir hes gonna help you back, just saying. He doesnt like Raphael. It has impact in Act 3 for sure.