Back and forth, and the DM stuck to his guns. Completely nerfed my entire concept, after weeks of play.
So, when people on online forums talk about how the DM is always right, and the campaign is 100% under the control of the DM and whatnot, it does tend to fly up my left nostril. Because, by the arguments put forward by [MENTION=6677017]Sword of Spirit[/MENTION] and others, I should have just nodded and smiled and not been the slightest put out by having a DM flush my character down the toilet. I made a character whose entire schtick was creating new spells. Not spend level after level trying to make a single third level spell for the entire campaign. Talk about frustrating.
I guess my basic point is, no, the campaign is not always 100% under the ownership of the DM. DM's make mistakes. DM's don't think of everything. None of us do. And putting your campaign world ahead of what the player's want is almost always (presuming good faith on the part of the player) a very bad idea. When your players are enthusiastic about an idea, run with it. If it runs roughshod over your campaign world? So what? Make up new stuff. That's what world building is all about.
My advice to DM's is to never presume that your ideas are better than those of your players.
Surely a GM changing the rules mid-game (bad) is different from a GM not letting a player
change rules, or even change fluff? If the rules had given you a 3% chance but you had
told the GM your concept required a 30% chance, he'd have been well within his rights to
say no and stick to RAW.