Maxperson
Morkus from Orkus
Everything is subject to fiat to a degree. Some is just more subject to it than others.Short of just not running the game, I have to disagree.
Sure. You can always leave the game.DM fiat is subject to player acceptance. When my PC gains a level, I choose what my PC gains as far as features, etc. If, prior to playing, the DM limits something and I agree to that limitation, then that is on me. If I choose not to, I can find another DM or just run my own game.
Unless the DM has set the room up so that healing is not possible for some reason. There's no such ability set up in the game, so the DM created it by fiat and put it into the dungeon. That would be a legitimate fiat reason for your Second Wind not to work. Now it's very hard to use fiat to in good faith stop something like Second Wind, but it's possible.DM fiat goes a long way, certainly, but if I decide to use Second Wind on my turn as my bonus action, there is really nothing the DM can do about it.