I am new to D&D 5th ed. I have purchased the books but not played in a group. One of the first big things I see is that advantage (or disadvantage) replace most of the die roll modifiers.
Is there EVER a case where more than 2 dice are rolled? (either adv. or disadv.)
I have seen the probability charts that display exactly what the 2nd d20 does on advantage or disadvantage, to your probability of rolling a certain number or higher. Is there ever a case, in the DMG, etc., where a DM might choose, or would be recommended to, ask player(s) to roll a 3rd die? (I.e., that those graphs should be a bit more sloped.)
Example: What if a rogue has a modifier that gives advantage to climb a wall. (feat, special gloves, etc.) If it is also raining, the wall is covered in algae, and he has a wounded thumb, do the + and - really just cancel out, so he has a straight chance? Or would these hypothetical disadvantages just add to the DC?